diff --git a/.gitignore b/.gitignore
index 1a5f7b618..ed3934e45 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,5 +30,6 @@
 
 # Executables
 *.exe
+a.out
 *.out
 *.app
diff --git a/.vscode/settings.json b/.vscode/settings.json
index 8b117a5fd..0ab2708d0 100644
--- a/.vscode/settings.json
+++ b/.vscode/settings.json
@@ -63,5 +63,9 @@
           "utility": "cpp",
           "valarray": "cpp",
           "algorithm": "cpp"
-     }
-}
\ No newline at end of file
+     },
+     "C_Cpp.clang_format_style": "{BasedOnStyle: Google, IndentWidth: 4, ColumnLimit: 80, UseTab: Never}",
+     "editor.formatOnSave": true,
+     "editor.formatOnType": true,
+     "editor.formatOnPaste": true
+}
diff --git a/CONTRIBUTION.md b/CONTRIBUTION.md
index adafa955a..9f0205bfd 100644
--- a/CONTRIBUTION.md
+++ b/CONTRIBUTION.md
@@ -12,8 +12,11 @@ We are very happy that you consider implementing algorithms and data structures
 - You submitted work fulfils or mostly fulfils our styles and standards.
 
 **New implementation** New implementation are welcome!
+
 **Improving comments** and **adding tests** to existing algorithms are much appreciated.
 
+**Issues** Please avoid opening issues asking to be "assigned” to a particular algorithm.  This merely creates unnecessary noise for maintainers.  Instead, please submit your implementation in a pull request and it will be evaluated by project maintainers.
+
 ### Making Changes
 
 #### Code
diff --git a/DIRECTORY.md b/DIRECTORY.md
index d9ca3ae36..9e36309dc 100644
--- a/DIRECTORY.md
+++ b/DIRECTORY.md
@@ -4,6 +4,7 @@
   * [Knight Tour](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/knight_tour.cpp)
   * [Minimax](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/minimax.cpp)
   * [N Queens](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/n_queens.cpp)
+  * [N Queens All Solution Optimised](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/n_queens_all_solution_optimised.cpp)
   * [Nqueen Print All Solutions](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/nqueen_print_all_solutions.cpp)
   * [Rat Maze](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/rat_maze.cpp)
   * [Sudoku Solve](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/backtracking/sudoku_solve.cpp)
@@ -13,6 +14,7 @@
   * [False-Position](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/computer_oriented_statistical_methods/false-position.cpp)
   * [Gaussian Elimination](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/computer_oriented_statistical_methods/Gaussian_elimination.cpp)
   * [Newton Raphson](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/computer_oriented_statistical_methods/Newton_Raphson.CPP)
+  * [Ordinary Least Squares Regressor](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/computer_oriented_statistical_methods/ordinary_least_squares_regressor.cpp)
   * [Secant Method](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/computer_oriented_statistical_methods/Secant_method.CPP)
   * [Successive Approximation](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/computer_oriented_statistical_methods/successive_approximation.CPP)
 
@@ -26,7 +28,7 @@
     * [Cll](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structure/cll/cll.h)
     * [Main Cll](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structure/cll/main_cll.cpp)
   * [Disjoint Set](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structure/disjoint_set.cpp)
-  * [Doubly Linked List](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structure/Doubly%20Linked%20List.cpp)
+  * [Doubly Linked List](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structure/doubly_linked_list.cpp)
   * [Linked List](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structure/linked_list.cpp)
   * [Linkedlist Implentation Usingarray](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structure/linkedList_implentation_usingArray.cpp)
   * [List Array](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/data_structure/List%20Array.cpp)
@@ -72,13 +74,19 @@
 
 ## Graph
   * [Bfs](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/BFS.cpp)
+  * [Bridge Finding With Tarjan Algorithm](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/bridge_finding_with_tarjan_algorithm.cpp)
+  * [Connected Components](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/connected_components.cpp)
+  * [Connected Components With Dsu](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/connected_components_with_dsu.cpp)
   * [Dfs](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/DFS.cpp)
   * [Dfs With Stack](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/DFS_with_stack.cc)
   * [Dijkstra](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/Dijkstra.cpp)
   * [Kosaraju](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/kosaraju.cpp)
   * [Kruskal](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/Kruskal.cpp)
   * [Lca](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/lca.cpp)
+  * [Max Flow With Ford Fulkerson And Edmond Karp Algo](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/max_flow_with_ford_fulkerson_and_edmond_karp_algo.cpp)
+  * [Prim](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/prim.cpp)
   * [Topological-Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/Topological-Sort.cpp)
+  * [Topological Sort By Kahns Algo](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/graph/topological_sort_by_kahns_algo.cpp)
 
 ## Greedy Algorithms
   * [Dijkstra](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/greedy_algorithms/Dijkstra.cpp)
@@ -95,9 +103,12 @@
 
 ## Math
   * [Binary Exponent](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/binary_exponent.cpp)
+  * [Double Factorial](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/double_factorial.cpp)
   * [Eulers Totient Function](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/eulers_totient_function.cpp)
+  * [Extended Euclid Algorithm](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/extended_euclid_algorithm.cpp)
   * [Factorial](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/factorial.cpp)
   * [Fast Power](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/fast_power.cpp)
+  * [Fibonacci](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/fibonacci.cpp)
   * [Greatest Common Divisor](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/greatest_common_divisor.cpp)
   * [Greatest Common Divisor Euclidean](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/greatest_common_divisor_euclidean.cpp)
   * [Modular Inverse Fermat Little Theorem](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/math/modular_inverse_fermat_little_theorem.cpp)
@@ -114,6 +125,7 @@
   * [Array Right Rotation](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/operations_on_datastructures/Array%20Right%20Rotation.cpp)
   * [Circular Linked List](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/operations_on_datastructures/Circular%20Linked%20List.cpp)
   * [Circular Queue Using Array](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/operations_on_datastructures/Circular%20Queue%20Using%20Array.cpp)
+  * [Get Size Of Linked List](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/operations_on_datastructures/get_size_of_linked_list.cpp)
   * [Intersection Of 2 Arrays](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/operations_on_datastructures/Intersection_of_2_arrays.cpp)
   * [Reverse A Linked List Using Recusion](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/operations_on_datastructures/Reverse%20a%20Linked%20List%20using%20Recusion.cpp)
   * [Selectionsortlinkedlist](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/operations_on_datastructures/selectionSortLinkedList.cpp)
@@ -146,6 +158,9 @@
 
 ## Probability
   * [Addition Rule](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/probability/addition_rule.cpp)
+  * [Bayes Theorem](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/probability/bayes_theorem.cpp)
+  * [Binomial Dist](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/probability/binomial_dist.cpp)
+  * [Poisson Dist](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/probability/poisson_dist.cpp)
 
 ## Range Queries
   * [Bit](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/range_queries/bit.cpp)
@@ -154,11 +169,12 @@
   * [Segtree](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/range_queries/segTree.cpp)
 
 ## Search
-  * [Binary Search](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/search/Binary%20Search.cpp)
+  * [Binary Search](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/search/binary_search.cpp)
   * [Exponential Search](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/search/exponential_search.cpp)
   * [Hash Search](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/search/hash_search.cpp)
   * [Interpolation Search](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/search/Interpolation%20Search.cpp)
   * [Interpolation Search](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/search/interpolation_search.cpp)
+  * [Jump Search](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/search/jump_search.cpp)
   * [Linear Search](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/search/Linear%20Search.cpp)
   * [Median Search](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/search/median_search.cpp)
   * [Searching](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/search/searching.cpp)
@@ -185,8 +201,10 @@
   * [Selection Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/Selection%20Sort.cpp)
   * [Shell Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/Shell%20Sort.cpp)
   * [Slow Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/Slow%20Sort.cpp)
+  * [Swap Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/swap_sort.cpp)
   * [Tim Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/Tim%20Sort.cpp)
 
 ## Strings
   * [Brute Force String Searching](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/strings/brute_force_string_searching.cpp)
   * [Knuth Morris Pratt](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/strings/knuth_morris_pratt.cpp)
+  * [Rabin Karp](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/strings/rabin_karp.cpp)
diff --git a/backtracking/n_queens_all_solution_optimised.cpp b/backtracking/n_queens_all_solution_optimised.cpp
new file mode 100644
index 000000000..1db730f63
--- /dev/null
+++ b/backtracking/n_queens_all_solution_optimised.cpp
@@ -0,0 +1,75 @@
+#include <iostream>
+#define n 4
+#define inc_loop(var, start, stop) for (int var=start; var <= stop; var++)
+#define dec_loop(var, start, stop) for (int var=start; var >= stop; var--)
+void PrintSol(int Board[n][n]) {
+    inc_loop(i, 0, n-1) {
+        inc_loop(j, 0, n-1)
+            std::cout << Board[i][j] << " ";
+        std::cout << std::endl;
+    }
+    std::cout << std::endl;
+    if (n%2 == 0 || (n%2 == 1 && Board[n/2+1][0] != 1)) {
+        inc_loop(i, 0, n-1) {
+            dec_loop(j, n-1, 0)
+                std::cout << Board[i][j] << " ";
+            std::cout << std::endl;
+        }
+        std::cout << std::endl;
+    }
+}
+
+bool CanIMove(int Board[n][n], int row, int col) {
+    /// check in the row
+    inc_loop(i, 0, col-1) {
+        if (Board[row][i] == 1)
+            return false;
+    }
+    /// check the first diagonal
+    for (int i = row, j = col; i >= 0 && j >= 0; i--, j--) {
+        if (Board[i][j] == 1)
+            return false;
+    }
+    /// check the second diagonal
+    for (int i = row, j = col; i <= n - 1 && j >= 0; i++, j--) {
+        if (Board[i][j] == 1)
+            return false;
+    }
+    return true;
+}
+
+void NQueenSol(int Board[n][n], int col) {
+    if (col >= n) {
+        PrintSol(Board);
+        return;
+    }
+    inc_loop(i, 0, n-1) {
+        if (CanIMove(Board, i, col)) {
+            Board[i][col] = 1;
+            NQueenSol(Board, col + 1);
+            Board[i][col] = 0;
+        }
+    }
+}
+
+int main() {
+    int Board[n][n] = {0};
+    if (n%2 == 0) {
+        inc_loop(i, 0, n/2-1) {
+            if (CanIMove(Board, i, 0)) {
+                Board[i][0] = 1;
+                NQueenSol(Board, 1);
+                Board[i][0] = 0;
+            }
+        }
+    } else {
+        inc_loop(i, 0, n/2) {
+            if (CanIMove(Board, i, 0)) {
+                Board[i][0] = 1;
+                NQueenSol(Board, 1);
+                Board[i][0] = 0;
+            }
+        }
+    }
+    return 0;
+}
diff --git a/computer_oriented_statistical_methods/ordinary_least_squares_regressor.cpp b/computer_oriented_statistical_methods/ordinary_least_squares_regressor.cpp
new file mode 100644
index 000000000..f50ccf1b1
--- /dev/null
+++ b/computer_oriented_statistical_methods/ordinary_least_squares_regressor.cpp
@@ -0,0 +1,349 @@
+/**
+ * Program that gets the number of data samples and number of features per
+ * sample along with output per sample. It applies OLS regression to compute
+ * the regression output for additional test data samples.
+ **/
+#include <iomanip>
+#include <iostream>
+#include <vector>
+
+template <typename T>
+std::ostream &operator<<(std::ostream &out,
+                         std::vector<std::vector<T>> const &v) {
+  const int width = 10;
+  const char separator = ' ';
+
+  for (size_t row = 0; row < v.size(); row++) {
+    for (size_t col = 0; col < v[row].size(); col++)
+      out << std::left << std::setw(width) << std::setfill(separator)
+          << v[row][col];
+    out << std::endl;
+  }
+
+  return out;
+}
+
+template <typename T>
+std::ostream &operator<<(std::ostream &out, std::vector<T> const &v) {
+  const int width = 15;
+  const char separator = ' ';
+
+  for (size_t row = 0; row < v.size(); row++)
+    out << std::left << std::setw(width) << std::setfill(separator) << v[row];
+
+  return out;
+}
+
+template <typename T>
+inline bool is_square(std::vector<std::vector<T>> const &A) {
+  // Assuming A is square matrix
+  size_t N = A.size();
+  for (size_t i = 0; i < N; i++)
+    if (A[i].size() != N)
+      return false;
+  return true;
+}
+
+/**
+ * matrix multiplication
+ **/
+template <typename T>
+std::vector<std::vector<T>> operator*(std::vector<std::vector<T>> const &A,
+                                      std::vector<std::vector<T>> const &B) {
+  // Number of rows in A
+  size_t N_A = A.size();
+  // Number of columns in B
+  size_t N_B = B[0].size();
+
+  std::vector<std::vector<T>> result(N_A);
+
+  if (A[0].size() != B.size()) {
+    std::cerr << "Number of columns in A != Number of rows in B ("
+              << A[0].size() << ", " << B.size() << ")" << std::endl;
+    return result;
+  }
+
+  for (size_t row = 0; row < N_A; row++) {
+    std::vector<T> v(N_B);
+    for (size_t col = 0; col < N_B; col++) {
+      v[col] = static_cast<T>(0);
+      for (size_t j = 0; j < B.size(); j++)
+        v[col] += A[row][j] * B[j][col];
+    }
+    result[row] = v;
+  }
+
+  return result;
+}
+
+template <typename T>
+std::vector<T> operator*(std::vector<std::vector<T>> const &A,
+                         std::vector<T> const &B) {
+  // Number of rows in A
+  size_t N_A = A.size();
+
+  std::vector<T> result(N_A);
+
+  if (A[0].size() != B.size()) {
+    std::cerr << "Number of columns in A != Number of rows in B ("
+              << A[0].size() << ", " << B.size() << ")" << std::endl;
+    return result;
+  }
+
+  for (size_t row = 0; row < N_A; row++) {
+    result[row] = static_cast<T>(0);
+    for (size_t j = 0; j < B.size(); j++)
+      result[row] += A[row][j] * B[j];
+  }
+
+  return result;
+}
+
+template <typename T>
+std::vector<float> operator*(float const scalar, std::vector<T> const &A) {
+  // Number of rows in A
+  size_t N_A = A.size();
+
+  std::vector<float> result(N_A);
+
+  for (size_t row = 0; row < N_A; row++) {
+    result[row] += A[row] * static_cast<float>(scalar);
+  }
+
+  return result;
+}
+
+template <typename T>
+std::vector<float> operator*(std::vector<T> const &A, float const scalar) {
+  // Number of rows in A
+  size_t N_A = A.size();
+
+  std::vector<float> result(N_A);
+
+  for (size_t row = 0; row < N_A; row++)
+    result[row] = A[row] * static_cast<float>(scalar);
+
+  return result;
+}
+
+template <typename T>
+std::vector<float> operator/(std::vector<T> const &A, float const scalar) {
+  return (1.f / scalar) * A;
+}
+
+template <typename T>
+std::vector<T> operator-(std::vector<T> const &A, std::vector<T> const &B) {
+  // Number of rows in A
+  size_t N = A.size();
+
+  std::vector<T> result(N);
+
+  if (B.size() != N) {
+    std::cerr << "Vector dimensions shouldbe identical!" << std::endl;
+    return A;
+  }
+
+  for (size_t row = 0; row < N; row++)
+    result[row] = A[row] - B[row];
+
+  return result;
+}
+
+template <typename T>
+std::vector<T> operator+(std::vector<T> const &A, std::vector<T> const &B) {
+  // Number of rows in A
+  size_t N = A.size();
+
+  std::vector<T> result(N);
+
+  if (B.size() != N) {
+    std::cerr << "Vector dimensions shouldbe identical!" << std::endl;
+    return A;
+  }
+
+  for (size_t row = 0; row < N; row++)
+    result[row] = A[row] + B[row];
+
+  return result;
+}
+
+/**
+ * Get matrix inverse using Row-trasnformations
+ **/
+template <typename T>
+std::vector<std::vector<float>>
+get_inverse(std::vector<std::vector<T>> const &A) {
+  // Assuming A is square matrix
+  size_t N = A.size();
+
+  std::vector<std::vector<float>> inverse(N);
+  for (size_t row = 0; row < N; row++) {
+    // preallocatae a resultant identity matrix
+    inverse[row] = std::vector<float>(N);
+    for (size_t col = 0; col < N; col++)
+      inverse[row][col] = (row == col) ? 1.f : 0.f;
+  }
+
+  if (!is_square(A)) {
+    std::cerr << "A must be a square matrix!" << std::endl;
+    return inverse;
+  }
+
+  // preallocatae a temporary matrix identical to A
+  std::vector<std::vector<float>> temp(N);
+  for (size_t row = 0; row < N; row++) {
+    std::vector<float> v(N);
+    for (size_t col = 0; col < N; col++)
+      v[col] = static_cast<float>(A[row][col]);
+    temp[row] = v;
+  }
+
+  // start transformations
+  for (size_t row = 0; row < N; row++) {
+    for (size_t row2 = row; row2 < N && temp[row][row] == 0; row2++) {
+      // this to ensure diagonal elements are not 0
+      temp[row] = temp[row] + temp[row2];
+      inverse[row] = inverse[row] + inverse[row2];
+    }
+
+    for (size_t col2 = row; col2 < N && temp[row][row] == 0; col2++) {
+      // this to further ensure diagonal elements are not 0
+      for (size_t row2 = 0; row2 < N; row2++) {
+        temp[row2][row] = temp[row2][row] + temp[row2][col2];
+        inverse[row2][row] = inverse[row2][row] + inverse[row2][col2];
+      }
+    }
+
+    if (temp[row][row] == 0) {
+      // Probably a low-rank matrix and hence singular
+      std::cerr << "Low-rank matrix, no inverse!" << std::endl;
+      return inverse;
+    }
+
+    // set diagonal to 1
+    float divisor = static_cast<float>(temp[row][row]);
+    temp[row] = temp[row] / divisor;
+    inverse[row] = inverse[row] / divisor;
+    // Row transformations
+    for (size_t row2 = 0; row2 < N; row2++) {
+      if (row2 == row)
+        continue;
+      float factor = temp[row2][row];
+      temp[row2] = temp[row2] - factor * temp[row];
+      inverse[row2] = inverse[row2] - factor * inverse[row];
+    }
+  }
+
+  return inverse;
+}
+
+/**
+ * matrix transpose
+ **/
+template <typename T>
+std::vector<std::vector<T>>
+get_transpose(std::vector<std::vector<T>> const &A) {
+  std::vector<std::vector<T>> result(A[0].size());
+
+  for (size_t row = 0; row < A[0].size(); row++) {
+    std::vector<T> v(A.size());
+    for (size_t col = 0; col < A.size(); col++)
+      v[col] = A[col][row];
+
+    result[row] = v;
+  }
+  return result;
+}
+
+template <typename T>
+std::vector<float> fit_OLS_regressor(std::vector<std::vector<T>> const &X,
+                                     std::vector<T> const &Y) {
+  // NxF
+  std::vector<std::vector<T>> X2 = X;
+  for (size_t i = 0; i < X2.size(); i++)
+    // add Y-intercept -> Nx(F+1)
+    X2[i].push_back(1);
+  // (F+1)xN
+  std::vector<std::vector<T>> Xt = get_transpose(X2);
+  // (F+1)x(F+1)
+  std::vector<std::vector<T>> tmp = get_inverse(Xt * X2);
+  // (F+1)xN
+  std::vector<std::vector<float>> out = tmp * Xt;
+  // cout << endl
+  //      << "Projection matrix: " << X2 * out << endl;
+
+  // Fx1,1    -> (F+1)^th element is the independent constant
+  return out * Y;
+}
+
+/**
+ * Given data and OLS model coeffficients, predict
+ * regression estimates
+ **/
+template <typename T>
+std::vector<float> predict_OLS_regressor(std::vector<std::vector<T>> const &X,
+                                         std::vector<float> const &beta) {
+  std::vector<float> result(X.size());
+
+  for (size_t rows = 0; rows < X.size(); rows++) {
+    // -> start with constant term
+    result[rows] = beta[X[0].size()];
+    for (size_t cols = 0; cols < X[0].size(); cols++)
+      result[rows] += beta[cols] * X[rows][cols];
+  }
+  // Nx1
+  return result;
+}
+
+int main() {
+  size_t N, F;
+
+  std::cout << "Enter number of features: ";
+  // number of features = columns
+  std::cin >> F;
+  std::cout << "Enter number of samples: ";
+  // number of samples = rows
+  std::cin >> N;
+
+  std::vector<std::vector<float>> data(N);
+  std::vector<float> Y(N);
+
+  std::cout
+      << "Enter training data. Per sample, provide features ad one output."
+      << std::endl;
+
+  for (size_t rows = 0; rows < N; rows++) {
+    std::vector<float> v(F);
+    std::cout << "Sample# " << rows + 1 << ": ";
+    for (size_t cols = 0; cols < F; cols++)
+      // get the F features
+      std::cin >> v[cols];
+    data[rows] = v;
+    // get the corresponding output
+    std::cin >> Y[rows];
+  }
+
+  std::vector<float> beta = fit_OLS_regressor(data, Y);
+  std::cout << std::endl << std::endl << "beta:" << beta << std::endl;
+
+  size_t T;
+  std::cout << "Enter number of test samples: ";
+  // number of test sample inputs
+  std::cin >> T;
+  std::vector<std::vector<float>> data2(T);
+  // vector<float> Y2(T);
+
+  for (size_t rows = 0; rows < T; rows++) {
+    std::cout << "Sample# " << rows + 1 << ": ";
+    std::vector<float> v(F);
+    for (size_t cols = 0; cols < F; cols++)
+      std::cin >> v[cols];
+    data2[rows] = v;
+  }
+
+  std::vector<float> out = predict_OLS_regressor(data2, beta);
+  for (size_t rows = 0; rows < T; rows++)
+    std::cout << out[rows] << std::endl;
+
+  return 0;
+}
diff --git a/data_structure/Doubly Linked List.cpp b/data_structure/Doubly Linked List.cpp
deleted file mode 100644
index 84a239d3f..000000000
--- a/data_structure/Doubly Linked List.cpp	
+++ /dev/null
@@ -1,134 +0,0 @@
-#include <iostream>
-using namespace std;
-
-struct node
-{
-	int val;
-	node *prev;
-	node *next;
-};
-
-node *start;
-
-void insert(int x)
-{
-	node *t = start;
-	if (start != NULL)
-	{
-		while (t->next != NULL)
-		{
-			t = t->next;
-		}
-		node *n = new node;
-		t->next = n;
-		n->prev = t;
-		n->val = x;
-		n->next = NULL;
-	}
-	else
-	{
-		node *n = new node;
-		n->val = x;
-		n->prev = NULL;
-		n->next = NULL;
-		start = n;
-	}
-}
-
-void remove(int x)
-{
-	node *t = start;
-	while (t->val != x)
-	{
-		t = t->next;
-	}
-	t->prev->next = t->next;
-	t->next->prev = t->prev;
-	delete t;
-}
-
-void search(int x)
-{
-	node *t = start;
-	int found = 0;
-	while (t != NULL)
-	{
-		if (t->val == x)
-		{
-			cout << "\nFound";
-			found = 1;
-			break;
-		}
-		t = t->next;
-	}
-	if (found == 0)
-	{
-		cout << "\nNot Found";
-	}
-}
-
-void show()
-{
-	node *t = start;
-	while (t != NULL)
-	{
-		cout << t->val << "\t";
-		t = t->next;
-	}
-}
-
-void reverseShow()
-{
-	node *t = start;
-	while (t->next != NULL)
-	{
-		t = t->next;
-	}
-	while (t != NULL)
-	{
-		cout << t->val << "\t";
-		t = t->prev;
-	}
-}
-
-int main()
-{
-	int choice, x;
-	do
-	{
-		cout << "\n1. Insert";
-		cout << "\n2. Delete";
-		cout << "\n3. Search";
-		cout << "\n4. Forward print";
-		cout << "\n5. Reverse print";
-		cout << "\n\nEnter you choice : ";
-		cin >> choice;
-		switch (choice)
-		{
-		case 1:
-			cout << "\nEnter the element to be inserted : ";
-			cin >> x;
-			;
-			insert(x);
-			break;
-		case 2:
-			cout << "\nEnter the element to be removed : ";
-			cin >> x;
-			remove(x);
-			break;
-		case 3:
-			cout << "\nEnter the element to be searched : ";
-			cin >> x;
-			search(x);
-			break;
-		case 4:
-			show();
-			break;
-		case 5:
-			reverseShow();
-			break;
-		}
-	} while (choice != 0);
-
-	return 0;
-}
diff --git a/data_structure/doubly_linked_list.cpp b/data_structure/doubly_linked_list.cpp
new file mode 100644
index 000000000..4fc38abfc
--- /dev/null
+++ b/data_structure/doubly_linked_list.cpp
@@ -0,0 +1,138 @@
+#include <iostream>
+#include<cstdio>
+#include<cstdlib>
+
+struct node {
+  int val;
+  node *prev;
+  node *next;
+}*start;
+
+class double_linked_list {
+ public:
+  double_linked_list() {
+    start = NULL;
+  }
+  void insert(int x);
+  void remove(int x);
+  void search(int x);
+  void show();
+  void reverseShow();
+};
+
+void double_linked_list::insert(int x) {
+  node *t = start;
+  if (start != NULL) {
+    while (t->next != NULL) {
+      t = t->next;
+    }
+    node *n = new node;
+    t->next = n;
+    n->prev = t;
+    n->val = x;
+    n->next = NULL;
+  } else {
+    node *n = new node;
+    n->val = x;
+    n->prev = NULL;
+    n->next = NULL;
+    start = n;
+  }
+}
+
+void double_linked_list::remove(int x) {
+  node *t = start;
+  while (t != NULL && t->val != x) {
+    t = t-> next;
+  }
+  if (t == NULL) {
+    return;
+  }
+  if (t->prev == NULL) {
+    if (t->next == NULL) {
+      start = NULL;
+    } else {
+      start = t->next;
+      start->prev = NULL;
+    }
+  } else if (t->next == NULL) {
+    t->prev->next = NULL;
+  } else {
+    t->prev->next = t->next;
+    t->next->prev = t->prev;
+  }
+  delete t;
+}
+
+void double_linked_list::search(int x) {
+  node *t = start;
+  int found = 0;
+  while (t != NULL) {
+    if (t->val == x) {
+      std::cout << "\nFound";
+      found = 1;
+      break;
+    }
+    t = t->next;
+  }
+  if (found == 0) {
+    std::cout << "\nNot Found";
+  }
+}
+
+void double_linked_list::show() {
+  node *t = start;
+  while (t != NULL) {
+    std::cout << t->val << "\t";
+    t = t->next;
+  }
+}
+
+void double_linked_list::reverseShow() {
+  node *t = start;
+  while (t != NULL && t->next != NULL) {
+    t = t->next;
+  }
+  while (t != NULL) {
+    std::cout << t->val << "\t";
+    t = t->prev;
+  }
+}
+
+int main() {
+  int choice, x;
+  double_linked_list ob;
+  do {
+    std::cout << "\n1. Insert";
+    std::cout << "\n2. Delete";
+    std::cout << "\n3. Search";
+    std::cout << "\n4. Forward print";
+    std::cout << "\n5. Reverse print";
+    std::cout << "\n\nEnter you choice : ";
+    std::cin >> choice;
+    switch (choice) {
+      case 1:
+        std::cout << "\nEnter the element to be inserted : ";
+        std::cin >> x;
+        ob.insert(x);
+        break;
+      case 2:
+        std::cout << "\nEnter the element to be removed : ";
+        std::cin >> x;
+        ob.remove(x);
+        break;
+      case 3:
+        std::cout << "\nEnter the element to be searched : ";
+        std::cin >> x;
+        ob.search(x);
+        break;
+      case 4:
+        ob.show();
+        break;
+      case 5:
+        ob.reverseShow();
+        break;
+    }
+  } while (choice != 0);
+  return 0;
+}
diff --git a/graph/bridge_finding_with_tarjan_algorithm.cpp b/graph/bridge_finding_with_tarjan_algorithm.cpp
new file mode 100644
index 000000000..ca124f512
--- /dev/null
+++ b/graph/bridge_finding_with_tarjan_algorithm.cpp
@@ -0,0 +1,79 @@
+/*
+ *  Copyright : 2020 , MIT
+ *  Author : Amit Kumar (offamitkumar)
+ *  Last Modified Date: May 24, 2020
+ *
+ */
+#include <vector>  //  for std::vector
+#include <algorithm>  //  for min & max
+#include <iostream>  //  for cout
+using std::vector;
+using std::cout;
+using std::min;
+class Solution {
+    vector < vector < int > > graph;
+    vector<int>in_time , out_time;
+    int timer;
+    vector < vector < int > > bridge;
+    vector<bool>visited;
+    void dfs(int current_node , int parent) {
+        visited.at(current_node) = true;
+        in_time[current_node] = out_time[current_node] = timer++;
+        for ( auto&itr : graph[current_node] ) {
+            if (itr == parent) {
+                continue;
+            }
+            if (!visited[itr]) {
+                dfs(itr , current_node);
+                if (out_time[itr] > in_time[current_node]) {
+                    bridge.push_back({itr, current_node});
+                }
+            }
+            out_time[current_node] = min(out_time[current_node], out_time[itr]);
+        }
+    }
+
+ public:
+    vector <vector <int> > search_bridges(int n,
+            const vector<vector<int>>& connections) {
+        timer = 0;
+        graph.resize(n);
+        in_time.assign(n, 0);
+        visited.assign(n, false);
+        out_time.assign(n, 0);
+        for (auto&itr : connections) {
+            graph.at(itr[0]).push_back(itr[1]);
+            graph.at(itr[1]).push_back(itr[0]);
+        }
+        dfs(0, -1);
+        return bridge;
+    }
+};
+int main(void) {
+    Solution s1;
+    int number_of_node = 5;
+    vector< vector <int> >node;
+    node.push_back({0, 1});
+    node.push_back({1, 3});
+    node.push_back({1, 2});
+    node.push_back({2, 4});
+    /*
+     *     0 <--> 1 <---> 2
+     *            ^       ^
+     *            |       |
+     *            |       |
+     *            \/     \/
+     *            3       4
+     *
+     *    In this graph there are 4 bridges [0,2] , [2,4] , [3,5] , [1,2]
+     *    
+     *    I assumed that the graph is bi-directional and connected.
+     *
+     */
+    vector< vector <int> > bridges = s1.search_bridges(number_of_node , node);
+    cout << bridges.size() << " bridges found!\n";
+    for (auto&itr : bridges) {
+        cout << itr[0] << " --> " << itr[1] << '\n';
+    }
+    return 0;
+}
diff --git a/graph/connected_components_with_dsu.cpp b/graph/connected_components_with_dsu.cpp
new file mode 100644
index 000000000..2c5c6dab5
--- /dev/null
+++ b/graph/connected_components_with_dsu.cpp
@@ -0,0 +1,55 @@
+#include <iostream>
+#include <vector>
+#include <set>
+
+int N;  // denotes number of nodes;
+std::vector<int> parent;
+std::vector<int> siz;
+void make_set() {  // function the initialize every node as it's own parent
+    for (int i = 1; i <= N; i++) {
+        parent[i] = i;
+        siz[i] = 1;
+    }
+}
+// To find the component where following node belongs to
+int find_set(int v) {
+    if (v == parent[v])
+        return v;
+    return parent[v] = find_set(parent[v]);
+}
+
+void union_sets(int a, int b) {  // To join 2 components to belong to one
+    a = find_set(a);
+    b = find_set(b);
+    if (a != b) {
+        if (siz[a] < siz[b])
+            std::swap(a, b);
+        parent[b] = a;
+        siz[a] += siz[b];
+    }
+}
+
+int no_of_connected_components() {  // To find total no of connected components
+    std::set<int> temp;  // temp set to count number of connected components
+    for (int i = 1; i <= N; i++)
+        temp.insert(find_set(i));
+    return temp.size();
+}
+
+// All critical/corner cases have been taken care of.
+// Input your required values: (not hardcoded)
+int main() {
+    std::cin >> N;
+    parent.resize(N + 1);
+    siz.resize(N + 1);
+    make_set();
+    int edges;
+    std::cin >> edges;  // no of edges in the graph
+    while (edges--) {
+        int node_a, node_b;
+        std::cin >> node_a >> node_b;
+        union_sets(node_a, node_b);
+    }
+    std::cout << no_of_connected_components() << std::endl;
+    return 0;
+}
diff --git a/graph/max_flow_with_ford_fulkerson_and_edmond_karp_algo.cpp b/graph/max_flow_with_ford_fulkerson_and_edmond_karp_algo.cpp
new file mode 100644
index 000000000..ee394d9f0
--- /dev/null
+++ b/graph/max_flow_with_ford_fulkerson_and_edmond_karp_algo.cpp
@@ -0,0 +1,122 @@
+/*
+ * Author: Amit Kumar
+ * Created: May 24, 2020
+ * Copyright: 2020, Open-Source
+ * Last Modified: May 25, 2020
+ */
+#include <iostream>
+#include <queue>
+#include <tuple>
+#include <algorithm>
+#include <bitset>
+#include <limits>
+#include <cstring>
+#include <vector>
+#include <utility>
+// std::max capacity of node in graph
+const int MAXN = 505;
+class Graph {
+    int residual_capacity[MAXN][MAXN];
+    int capacity[MAXN][MAXN];  //  used while checking the flow of edge
+    int total_nodes;
+    int total_edges, source, sink;
+    int parent[MAXN];
+    std::vector <std::tuple <int, int, int> >edge_participated;
+    std::bitset <MAXN> visited;
+    int max_flow = 0;
+    bool bfs(int source, int sink) {  //  to find the augmented - path
+        memset(parent, -1, sizeof(parent));
+        visited.reset();
+        std::queue<int>q;
+        q.push(source);
+        bool is_path_found = false;
+        while (q.empty() == false && is_path_found == false) {
+            int current_node = q.front();
+            visited.set(current_node);
+            q.pop();
+            for (int i = 0; i < total_nodes; ++i) {
+                if (residual_capacity[current_node][i] > 0 && !visited[i]) {
+                    visited.set(i);
+                    parent[i] = current_node;
+                    if (i == sink) {
+                        return true;
+                    }
+                    q.push(i);
+                }
+            }
+        }
+        return false;
+    }
+
+ public:
+    Graph() {
+        memset(residual_capacity, 0, sizeof(residual_capacity));
+    }
+    void set_graph(void) {
+        std::cin >> total_nodes >> total_edges >> source >> sink;
+        for (int start, destination, capacity_, i = 0; i < total_edges; ++i) {
+            std::cin >> start >> destination >> capacity_;
+            residual_capacity[start][destination] = capacity_;
+            capacity[start][destination] = capacity_;
+        }
+    }
+    void ford_fulkerson(void) {
+        while (bfs(source, sink)) {
+            int current_node = sink;
+            int flow = std::numeric_limits<int>::max();
+            while (current_node != source) {
+                int parent_ = parent[current_node];
+                flow = std::min(flow, residual_capacity[parent_][current_node]);
+                current_node = parent_;
+            }
+            current_node = sink;
+            max_flow += flow;
+            while ( current_node != source ) {
+                int parent_ = parent[current_node];
+                residual_capacity[parent_][current_node] -= flow;
+                residual_capacity[current_node][parent_] += flow;
+                current_node = parent_;
+            }
+        }
+    }
+    void print_flow_info(void) {
+        for (int i = 0; i < total_nodes; ++i) {
+            for (int j = 0; j < total_nodes; ++j) {
+                if (capacity[i][j] &&
+                        residual_capacity[i][j] < capacity[i][j]) {
+                    edge_participated.push_back(
+                            std::make_tuple(i, j,
+                                capacity[i][j]-residual_capacity[i][j]));
+                }
+            }
+        }
+        std::cout << "\nNodes : " << total_nodes
+            << "\nMax flow: " << max_flow
+            << "\nEdge present in flow: " << edge_participated.size()
+            << '\n';
+        std::cout<< "\nSource\tDestination\tCapacity\total_nodes";
+        for (auto&edge_data : edge_participated) {
+            int source, destination, capacity_;
+            std::tie(source, destination, capacity_) = edge_data;
+            std::cout << source << "\t" << destination << "\t\t"
+                      << capacity_ <<'\t';
+        }
+    }
+};
+int main(void) {
+    /*
+       Input Graph: (for testing )
+        4 5 0 3
+        0 1 10
+        1 2 1
+        1 3 1
+        0 2 1
+        2 3 10
+     */
+    Graph graph;
+    graph.set_graph();
+    graph.ford_fulkerson();
+    graph.print_flow_info();
+    return 0;
+}
+
diff --git a/graph/prim.cpp b/graph/prim.cpp
new file mode 100644
index 000000000..2923b5b25
--- /dev/null
+++ b/graph/prim.cpp
@@ -0,0 +1,58 @@
+// C++ program to implement Prim's Algorithm
+#include <iostream>
+#include <vector>
+#include <queue>
+
+const int MAX = 1e4 + 5;
+typedef std:: pair<int, int> PII;
+
+bool marked[MAX];
+std:: vector <PII> adj[MAX];
+
+int prim(int x) {
+    // priority queue to maintain edges with respect to weights
+    std:: priority_queue<PII, std:: vector<PII>, std:: greater<PII> > Q;
+    int y;
+    int minimumCost = 0;
+    PII p;
+
+    Q.push(std:: make_pair(0, x));
+    while (!Q.empty()) {
+        // Select the edge with minimum weight
+        p = Q.top();
+        Q.pop();
+        x = p.second;
+        // Checking for cycle
+        if (marked[x] == true)
+            continue;
+        minimumCost += p.first;
+        marked[x] = true;
+        for (int i = 0; i < adj[x].size(); ++i) {
+            y = adj[x][i].second;
+            if (marked[y] == false)
+                Q.push(adj[x][i]);
+        }
+    }
+    return minimumCost;
+}
+
+int main() {
+    int nodes, edges, x, y;
+    int weight, minimumCost;
+
+    std:: cin >> nodes >> edges;  // number of nodes & edges in graph
+    if (nodes == 0 || edges == 0)
+        return 0;
+
+    // Edges with their nodes & weight
+    for (int i = 0; i < edges; ++i) {
+        std::cin >> x >> y >> weight;
+        adj[x].push_back(std:: make_pair(weight, y));
+        adj[y].push_back(std:: make_pair(weight, x));
+    }
+
+    // Selecting 1 as the starting node
+    minimumCost = prim(1);
+    std:: cout << minimumCost << std:: endl;
+    return 0;
+}
diff --git a/graph/topological_sort_by_kahns_algo.cpp b/graph/topological_sort_by_kahns_algo.cpp
new file mode 100644
index 000000000..eda2a74bc
--- /dev/null
+++ b/graph/topological_sort_by_kahns_algo.cpp
@@ -0,0 +1,68 @@
+#include <stdio.h>
+#include <string.h>
+#include <iostream>
+#include <vector>
+#include <queue>
+
+int *topoSortKahn(int N, std::vector<int> adj[]);
+
+int main() {
+    int nodes, edges;
+    std::cin >> edges >> nodes;
+    if (edges == 0 || nodes == 0)
+        return 0;
+    int u, v;
+
+    std::vector<int>graph[nodes];
+    // create graph
+    // example
+    // 6 6
+    // 5 0 5 2 2 3 4 0 4 1 1 3
+
+    for (int i = 0; i < edges; i++) {
+        std::cin >> u >> v;
+        graph[u].push_back(v);
+    }
+
+    int *topo = topoSortKahn(nodes, graph);
+    // topologically sorted nodes
+    for (int i = 0; i < nodes; i++) {
+        std::cout << topo[i] << " ";
+    }
+}
+
+int* topoSortKahn(int V, std::vector<int> adj[]) {
+    std::vector<bool>vis(V+1, false);
+    std::vector<int>deg(V+1, 0);
+    for (int i = 0; i < V; i++) {
+        for (int j = 0; j < adj[i].size(); j++) {
+            deg[adj[i][j]]++;
+        }
+    }
+    std::queue<int>q;
+    for (int i = 0; i < V; i++) {
+        if (deg[i] == 0) {
+            q.push(i);
+            vis[i] = true;
+        }
+    }
+    int *arr = new int[V+1];
+    memset(arr, 0, V+1);
+    int count = 0;
+    while (!q.empty()) {
+        int cur = q.front();
+        q.pop();
+        arr[count] = cur;
+        count++;
+        for (int i = 0; i < adj[cur].size(); i++) {
+            if (!vis[adj[cur][i]]) {
+                deg[adj[cur][i]]--;
+                if (deg[adj[cur][i]] == 0) {
+                    q.push(adj[cur][i]);
+                    vis[adj[cur][i]] = true;
+                }
+            }
+        }
+    }
+    return arr;
+}
diff --git a/math/double_factorial.cpp b/math/double_factorial.cpp
new file mode 100644
index 000000000..7b0d1d970
--- /dev/null
+++ b/math/double_factorial.cpp
@@ -0,0 +1,28 @@
+#include <iostream>
+#include <cassert>
+
+/* Double factorial of a non-negative integer n, is defined as the product of 
+all the integers from 1 to n that have the same parity (odd or even) as n.
+It is also called as semifactorial of a number and is denoted by !! */
+
+uint64_t double_factorial_iterative(uint64_t n) {
+  uint64_t res = 1;
+  for ( uint64_t i = n; i >= 0; i -= 2 ) {
+    if (i == 0 || i == 1) return res;
+    res *= i;
+  }
+}
+
+/* Recursion can be costly for large numbers */
+
+uint64_t double_factorial_recursive(uint64_t n) {
+  if (n <= 1) return 1;
+  return n * double_factorial_recursive(n - 2);
+}
+
+int main() {
+  uint64_t n{};
+  std::cin >> n;
+  assert(n >= 0);
+  std::cout << double_factorial_iterative(n);
+}
diff --git a/math/extended_euclid_algorithm.cpp b/math/extended_euclid_algorithm.cpp
new file mode 100644
index 000000000..3db14802f
--- /dev/null
+++ b/math/extended_euclid_algorithm.cpp
@@ -0,0 +1,28 @@
+#include <iostream>
+// Finding coefficients of a and b ie x and y in gcd(a, b) = a * x + b * y
+// d is gcd(a, b)
+// This is also used in finding Modular multiplicative inverse of a number.
+// (A * B)%M == 1 Here B is the MMI of A for given M,
+// so extendedEuclid (A, M) gives B.
+
+int d, x, y;
+void extendedEuclid(int A, int B) {
+    if (B == 0) {
+        d = A;
+        x = 1;
+        y = 0;
+    } else {
+        extendedEuclid(B, A%B);
+        int temp = x;
+        x = y;
+        y = temp - (A/B)*y;
+    }
+}
+
+int main() {
+    int a, b;
+    std::cin >> a >> b;
+    extendedEuclid(a, b);
+    std::cout << x << " " << y << std::endl;
+    return 0;
+}
diff --git a/math/fibonacci.cpp b/math/fibonacci.cpp
new file mode 100644
index 000000000..1c07cd93f
--- /dev/null
+++ b/math/fibonacci.cpp
@@ -0,0 +1,25 @@
+#include <iostream>
+#include <cassert>
+
+/* Calculate the the value on Fibonacci's sequence given an
+integer as input
+Fibonacci =  0, 1, 1, 2, 3, 5,
+             8, 13, 21, 34, 55,
+             89, 144, ...       */
+
+int fibonacci(uint n) {
+    /* If the input is 0 or 1 just return the same
+       This will set the first 2 values of the sequence */
+    if (n <= 1)
+        return n;
+
+    /* Add the last 2 values of the sequence to get next */
+    return fibonacci(n-1) + fibonacci(n-2);
+}
+
+int main() {
+    int n;
+    std::cin >> n;
+    assert(n >= 0);
+    std::cout << "F(" << n << ")= " << fibonacci(n) << std::endl;
+}
diff --git a/math/sqrt_double.cpp b/math/sqrt_double.cpp
index e3418bfc3..5a0fd1c88 100644
--- a/math/sqrt_double.cpp
+++ b/math/sqrt_double.cpp
@@ -6,6 +6,9 @@ number in O(logn) time,
 with precision fixed */
 
 double Sqrt(double x) {
+    if ( x > 0 && x < 1 ) {
+        return 1/Sqrt(1/x);
+    }
     double l = 0, r = x;
     /* Epsilon is the precision. 
     A great precision is 
diff --git a/operations_on_datastructures/get_size_of_linked_list.cpp b/operations_on_datastructures/get_size_of_linked_list.cpp
new file mode 100644
index 000000000..84f8db07f
--- /dev/null
+++ b/operations_on_datastructures/get_size_of_linked_list.cpp
@@ -0,0 +1,36 @@
+#include <iostream>
+
+class Node {
+ public:
+    int val;
+    Node *next;
+
+    Node(int v, Node *n) : val(v), next(n) {}  // Default constructor for Node
+};
+
+int getSize(Node *root) {
+    if (root == NULL) {
+        return 0;
+    }
+    // Each node will return 1 so the total adds up to be the size
+    return 1 + getSize(root->next);
+}
+
+int main() {
+    Node *myList = new Node(0, NULL);  // Initializes the LinkedList
+    Node *temp = myList;
+    // Creates a linked lists of total size 10, numbered 1 - 10
+    for (int i = 1; i < 10; i++) {
+        temp->next = new Node(i, NULL);
+        temp = temp->next;
+    }
+    // Creating other lists for checking purposes
+    Node *secondList = new Node(0, NULL);  // List of size 1
+    Node *thirdList = NULL;                // List of size 0
+
+    std::cout << getSize(myList) << std::endl
+              << getSize(secondList) << std::endl
+              << getSize(thirdList) << std::endl;
+
+    return 0;
+}
diff --git a/probability/bayes_theorem.cpp b/probability/bayes_theorem.cpp
new file mode 100644
index 000000000..d30be6c9a
--- /dev/null
+++ b/probability/bayes_theorem.cpp
@@ -0,0 +1,30 @@
+#include <iostream>
+
+// bayes' theorem > https://en.wikipedia.org/wiki/Bayes%27_theorem
+
+// bayes' theorem allows one to find P(A|B) given P(B|A)
+// or P(B|A) given P(A|B) and P(A) and P(B)
+
+// note P(A|B) is read 'The probability of A given that the event B has occured'
+
+// returns P(A|B)
+
+double bayes_AgivenB(double BgivenA, double A, double B) {
+    return (BgivenA * A) / B;
+}
+
+// returns P(B|A)
+
+double bayes_BgivenA(double AgivenB, double A, double B) {
+    return (AgivenB * B) / A;
+}
+
+int main() {
+    double A = 0.01;
+    double B = 0.1;
+    double BgivenA = 0.9;
+    double AgivenB = bayes_AgivenB(BgivenA, A, B);
+    std::cout << "A given B = " << AgivenB << std::endl;
+    std::cout << "B given A = " << bayes_BgivenA(AgivenB, A, B) << std::endl;
+    return 0;
+}
diff --git a/probability/binomial_dist.cpp b/probability/binomial_dist.cpp
new file mode 100644
index 000000000..b21a3e0fc
--- /dev/null
+++ b/probability/binomial_dist.cpp
@@ -0,0 +1,81 @@
+#include <iostream>
+#include <cmath>
+
+// the binomial distribution models the number of
+// successes in a sequence of n independent events
+
+// n : number of trials
+// p : probability of success
+// x : desired successes
+
+// finds the expected value of a binomial distribution
+
+double binomial_expected(double n, double p) {
+    return n * p;
+}
+
+// finds the variance of the binomial distribution
+
+double binomial_variance(double n, double p) {
+    return n * p * (1 - p);
+}
+
+// finds the standard deviation of the binomial distribution
+
+double binomial_standard_deviation(double n, double p) {
+    return sqrt(binomial_variance(n, p));
+}
+
+// Computes n choose r
+// n being the trials and r being the desired successes
+
+double nCr(double n, double r) {
+    double numerator = n;
+    double denominator = r;
+
+    for (int i = n - 1 ; i >= ((n - r) + 1); i--) {
+        numerator *= i;
+    }
+
+    for (int i = 1; i < r ; i++) {
+        denominator *= i;
+    }
+
+    return numerator / denominator;
+}
+
+// calculates the probability of exactly x successes
+
+double binomial_x_successes(double n, double p, double x) {
+    return nCr(n, x) * pow(p, x) * pow(1-p, n-x);
+}
+
+// calculates the probability of a result within a range (inclusive, inclusive)
+
+double binomial_range_successes(
+    double n, double p, double lower_bound, double upper_bound) {
+    double probability = 0;
+    for (int i = lower_bound; i <= upper_bound; i++) {
+        probability += nCr(n, i) * pow(p, i) * pow(1 - p, n - i);
+    }
+    return probability;
+}
+
+int main() {
+    std::cout << "expected value : "
+        <<binomial_expected(100, 0.5) << std::endl;
+
+    std::cout << "variance : "
+        << binomial_variance(100, 0.5) << std::endl;
+
+    std::cout << "standard deviation : "
+        << binomial_standard_deviation(100, 0.5) << std::endl;
+
+    std::cout << "exactly 30 successes : "
+        << binomial_x_successes(100, 0.5, 30) << std::endl;
+
+    std::cout << "45 or more successes : "
+        << binomial_range_successes(100, 0.5, 45, 100) << std::endl;
+
+    return 0;
+}
diff --git a/probability/poisson_dist.cpp b/probability/poisson_dist.cpp
new file mode 100644
index 000000000..345363368
--- /dev/null
+++ b/probability/poisson_dist.cpp
@@ -0,0 +1,66 @@
+#include <iostream>
+#include <cmath>
+
+// The Poisson distribution counts how many
+// events occur over a set time interval
+// https://en.wikipedia.org/wiki/Poisson_distribution
+
+// calculate the events per unit time
+// e.g 5 dollars every 2 mins = 5 / 2 = 2.5
+
+double poisson_rate(double events, double timeframe) {
+    return events / timeframe;
+}
+
+// calculate the expected value over a time
+// e.g rate of 2.5 over 10 mins = 2.5 x 10 = 25
+
+double poisson_expected(double rate, double time) {
+    return rate * time;
+}
+
+// find the factorial of a given number
+
+double fact(double x) {
+    double x_fact = x;
+    for (int i = x - 1; i > 0; i--) {
+        x_fact *= i;
+    }
+
+    if (x_fact <= 0) {
+        x_fact = 1;
+    }
+    return x_fact;
+}
+
+// find the probability of x successes in a Poisson dist
+
+double poisson_x_successes(double expected, double x) {
+    return (pow(expected, x) * exp(-expected)) / fact(x);
+}
+
+// probability of a success in range for Poisson dist (inclusive, inclusive)
+
+double poisson_range_successes(double expected, double lower, double upper) {
+    double probability = 0;
+    for (int i = lower; i <= upper; i++) {
+        probability += poisson_x_successes(expected, i);
+    }
+    return probability;
+}
+
+int main() {
+    double rate, expected;
+    rate = poisson_rate(3, 1);
+    std::cout << "Poisson rate : " << rate << std::endl;
+
+    expected = poisson_expected(rate, 2);
+    std::cout << "Poisson expected : " << expected << std::endl;
+
+    std::cout << "Poisson 0 successes : "
+        <<poisson_x_successes(expected, 0) <<std::endl;
+    std::cout << "Poisson 0-8 successes : "
+        << poisson_range_successes(expected, 0, 8) <<std::endl;
+
+    return 0;
+}
diff --git a/search/Binary Search.cpp b/search/Binary Search.cpp
deleted file mode 100644
index 2e90855e8..000000000
--- a/search/Binary Search.cpp	
+++ /dev/null
@@ -1,36 +0,0 @@
-#include <iostream>
-using namespace std;
-int binary_search(int a[], int l, int r, int key)
-{
-	while (l <= r)
-	{
-		int m = l + (r - l) / 2;
-		if (key == a[m])
-			return m;
-		else if (key < a[m])
-			r = m - 1;
-		else
-			l = m + 1;
-	}
-	return -1;
-}
-int main(int argc, char const *argv[])
-{
-	int n, key;
-	cout << "Enter size of array: ";
-	cin >> n;
-	cout << "Enter array elements: ";
-	int a[n];
-	for (int i = 0; i < n; ++i)
-	{
-		cin >> a[i];
-	}
-	cout << "Enter search key: ";
-	cin >> key;
-	int res = binary_search(a, 0, n - 1, key);
-	if (res != -1)
-		cout << key << " found at index " << res << endl;
-	else
-		cout << key << " not found" << endl;
-	return 0;
-}
\ No newline at end of file
diff --git a/search/binary_search.cpp b/search/binary_search.cpp
new file mode 100644
index 000000000..9933c9816
--- /dev/null
+++ b/search/binary_search.cpp
@@ -0,0 +1,34 @@
+#include <iostream>
+// binary_search function
+int binary_search(int a[], int l, int r, int key) {
+    while (l <= r) {
+          int m = l + (r - l) / 2;
+          if (key == a[m])
+              return m;
+          else if (key < a[m])
+               r = m - 1;
+          else
+              l = m + 1;
+          }
+          return -1;
+     }
+int main(int argc, char const* argv[]) {
+    int n, key;
+    std::cout << "Enter size of array: ";
+    std::cin >> n;
+    std::cout << "Enter array elements: ";
+    int* a = new int[n];
+// this loop use for store value in Array
+    for (int i = 0; i < n; i++) {
+        std::cin >> a[i];
+        }
+    std::cout << "Enter search key: ";
+    std::cin >> key;
+// this is use for find value in given array
+    int res = binary_search(a, 0, n - 1, key);
+    if (res != -1)
+       std::cout << key << " found at index " << res << std::endl;
+    else
+       std::cout << key << " not found" << std::endl;
+    return 0;
+}
diff --git a/search/jump_search.cpp b/search/jump_search.cpp
new file mode 100644
index 000000000..0ee7e4e00
--- /dev/null
+++ b/search/jump_search.cpp
@@ -0,0 +1,54 @@
+// C++ program to implement Jump Search
+
+#include <bits/stdc++.h>
+using namespace std;
+
+int jumpSearch(int arr[], int x, int n)
+{
+    // Finding block size to be jumped
+    int step = sqrt(n);
+
+    // Finding the block where element is
+    // present (if it is present)
+    int prev = 0;
+    while (arr[min(step, n)-1] < x)
+    {
+        prev = step;
+        step += sqrt(n);
+        if (prev >= n)
+            return -1;
+    }
+
+    // Doing a linear search for x in block
+    // beginning with prev.
+    while (arr[prev] < x)
+    {
+        prev++;
+
+        // If we reached next block or end of
+        // array, element is not present.
+        if (prev == min(step, n))
+            return -1;
+    }
+    // If element is found
+    if (arr[prev] == x)
+        return prev;
+
+    return -1;
+}
+
+// Driver program to test function
+int main()
+{
+    int arr[] = { 0, 1, 1, 2, 3, 5, 8, 13, 21,
+                34, 55, 89, 144, 233, 377, 610 };
+    int x = 55;
+    int n = sizeof(arr) / sizeof(arr[0]);
+
+    // Find the index of 'x' using Jump Search
+    int index = jumpSearch(arr, x, n);
+
+    // Print the index where 'x' is located
+    cout << "\nNumber " << x << " is at index " << index;
+    return 0;
+}
diff --git a/sorting/swap_sort.cpp b/sorting/swap_sort.cpp
new file mode 100644
index 000000000..a4ab1e57b
--- /dev/null
+++ b/sorting/swap_sort.cpp
@@ -0,0 +1,66 @@
+// C++ program to find minimum number of swaps required to sort an array
+#include <algorithm>
+#include <iostream>
+#include <utility>
+#include <vector>
+
+// Function returns the minimum number of swaps
+// required to sort the array
+int minSwaps(int arr[], int n) {
+    // Create an array of pairs where first
+    // element is array element and second element
+    // is position of first element
+    std::pair<int, int> arrPos[n];
+    for (int i = 0; i < n; i++) {
+        arrPos[i].first = arr[i];
+        arrPos[i].second = i;
+    }
+
+    // Sort the array by array element values to
+    // get right position of every element as second
+    // element of pair.
+    std::sort(arrPos, arrPos + n);
+
+    // To keep track of visited elements. Initialize
+    // all elements as not visited or false.
+    std::vector<bool> vis(n, false);
+
+    // Initialize result
+    int ans = 0;
+
+    // Traverse array elements
+    for (int i = 0; i < n; i++) {
+        // already swapped and corrected or
+        // already present at correct pos
+        if (vis[i] || arrPos[i].second == i)
+            continue;
+
+        // find out the number of node in
+        // this cycle and add in ans
+        int cycle_size = 0;
+        int j = i;
+        while (!vis[j]) {
+            vis[j] = 1;
+
+            // move to next node
+            j = arrPos[j].second;
+            cycle_size++;
+        }
+
+        // Update answer by adding current cycle.
+        if (cycle_size > 0) {
+            ans += (cycle_size - 1);
+        }
+    }
+
+    // Return result
+    return ans;
+}
+
+// program to test
+int main() {
+    int arr[] = {6, 7, 8, 1, 2, 3, 9, 12};
+    int n = (sizeof(arr) / sizeof(int));
+    std::cout << minSwaps(arr, n);
+    return 0;
+}
diff --git a/strings/rabin_karp.cpp b/strings/rabin_karp.cpp
new file mode 100644
index 000000000..62e3691c1
--- /dev/null
+++ b/strings/rabin_karp.cpp
@@ -0,0 +1,78 @@
+/*
+ * file name : rabin_karp.cpp
+ * author    : Amit Kumar 
+ * Copyright : 2020 , Amit Kumar 
+ * version   : 1.0
+ */
+#include<cassert>
+#include<cmath>
+#include<iostream>
+#include<string>
+
+using std::string;
+using std::pow;
+
+#define PRIME 5
+
+int64_t create_hash(string s , int n) {
+    int64_t result = 0;
+    for ( int i = 0; i < n; ++i ) {
+        result += (int64_t)(s[i] * (int64_t)pow(PRIME , i));
+    }
+    return result;
+}
+
+int64_t recalculate_hash(string s , int old_index ,
+        int new_index , int64_t old_hash , int patLength) {
+    int64_t new_hash = old_hash - s[old_index];
+    new_hash /= PRIME;
+    new_hash += (int64_t)(s[new_index]*(int64_t)pow(PRIME, patLength-1));
+    return new_hash;
+}
+
+bool check_if_equal(string str1 , string str2 ,
+                    int start1 , int end1 ,
+                    int start2 , int end2) {
+    if (end1-start1 != end2-start2) {
+        return false;
+    }
+    while (start1 <= end1 && start2 <= end2) {
+        if (str1[start1] != str2[start2]) {
+            return false;
+        }
+        start1++;
+        start2++;
+    }
+    return true;
+}
+
+/*
+ *  @description : search pattern in the given text 
+ *  @param : string str
+ *  @param : string pat
+ *  @return index of first occurrence of pattern or -1 if pattern not found
+ */
+
+int rabin_karp(const string &str , const string& pat) {
+    int64_t pat_hash = create_hash(pat , pat.size());
+    int64_t str_hash = create_hash(str , pat.size());
+    for (int i=0;  i <= str.size()-pat.size(); ++i) {
+        if (pat_hash == str_hash &&
+            check_if_equal(str , pat , i , i+pat.size()-1 , 0 , pat.size()-1)) {
+                return i;
+        }
+        if (i < str.size()-pat.size()) {
+            str_hash =
+                recalculate_hash(str, i, i+pat.size(), str_hash, pat.size());
+        }
+    }
+    return -1;  // return -1 if given pattern not found
+}
+
+int main(void) {
+    assert(rabin_karp("helloWorld", "world")    == -1);
+    assert(rabin_karp("helloWorld", "World")    ==  5);
+    assert(rabin_karp("this_is_c++" , "c++")   ==  8);
+    assert(rabin_karp("happy_coding", "happy") ==  0);
+    return 0;
+}