feat: Add Pancake Sort algorithm (#1189)

* Create pancake_sort.cpp

* Update pancake_sort.cpp

* Update pancake_sort.cpp

* Update pancake_sort.cpp

* Update pancake_sort.cpp

* Update pancake_sort.cpp

* Update pancake_sort.cpp

* Update pancake_sort.cpp

* Update pancake_sort.cpp

* updating DIRECTORY.md

* Update pancake_sort.cpp

* Update pancake_sort.cpp

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

DIRECTORY.md

@@ -248,6 +248,7 @@
   * [Non Recursive Merge Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/non_recursive_merge_sort.cpp)
   * [Numeric String Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/numeric_string_sort.cpp)
   * [Odd Even Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/odd_even_sort.cpp)
+  * [Pancake Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/pancake_sort.cpp)
   * [Pigeonhole Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/pigeonhole_sort.cpp)
   * [Quick Sort](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/quick_sort.cpp)
   * [Quick Sort 3](https://github.com/TheAlgorithms/C-Plus-Plus/blob/master/sorting/quick_sort_3.cpp)

sorting/pancake_sort.cpp

@@ -0,0 +1,129 @@
+/**
+ * @file
+ * @brief pancake sort sorts a disordered stack of pancakes by flipping any number of pancakes using a spatula using minimum number of flips.
+ *
+ * @details
+ * Unlike a traditional sorting algorithm, which attempts to sort with the fewest comparisons possible,
+ * the goal is to sort the sequence in as few reversals as possible.
+ * Overall time complexity of pancake sort is O(n^2)
+ * For example: example 1:-
+ * Disordered pancake sizes: {2,5,3,7,8}
+ * Sorted: {2,3,5,7,8}
+ * For example: example 2:-
+ * Disordered pancake sizes: {22,51,37,73,81}
+ * Sorted: {22,37,51,73,81}
+ * @author [Divyansh Gupta](https://github.com/divyansh12323)
+ * @see more on [Pancake sort](https://en.wikipedia.org/wiki/Pancake_sorting)
+ * @see related problem at [Leetcode](https://leetcode.com/problems/pancake-sorting/)
+*/
+
+#include <iostream>   // for io operations
+#include <vector>     // for std::vector
+#include <algorithm>  // for std::is_sorted
+#include <cassert>    // for std::assert
+
+/**
+ * @namespace sorting
+ * @brief Sorting algorithms
+ */
+namespace sorting {
+/**
+ * @namespace pancake_sort
+ * @brief Functions for [Pancake sort](https://en.wikipedia.org/wiki/Pancake_sorting) algorithm
+ */
+namespace pancake_sort {
+    /**
+    * @brief This implementation is for reversing elements in a a C-style array .
+    * @param [start,end] arr our vector of elements.
+    * @param start starting index of array
+    * @param end ending index of array
+    * @returns void
+    */
+    template<typename T>
+    void reverse(std::vector<T> &arr, int start, int end) {
+        T temp; //Temporary variable
+        while (start <= end) {
+            temp = arr[start];
+            arr[start] = arr[end];
+            arr[end] = temp;
+            start++;
+            end--;
+        }
+    }
+    /**
+    * @brief This implementation is for a C-style array input that gets modified in place.
+    * @param [start,end] arr our vector of elements.
+    * @param size size of given array
+    * @returns 0 on exit
+    */
+    template<typename T>
+    int pancakeSort(std::vector<T> &arr, int size) {
+        for (int i = size; i > 1; --i) {
+            int max_index = 0, j; //intialize some variables.
+            T max_value = 0;
+            for (j = 0; j < i; j++) {
+                if (arr[j] >= max_value) {
+                    max_value = arr[j];
+                    max_index = j;
+                }
+            }
+            if (max_index != i - 1) //check for reversing
+            {
+                reverse(arr, 0, max_index);
+                reverse(arr, 0, i - 1);
+            }
+        }
+        return 0;
+    }
+}  // namespace pancake_sort
+}  // namespace sorting
+
+/**
+ * @brief Test implementations
+ * @returns void
+ */
+static void test() {
+    // example 1: vector of int
+    const int size1 = 7;
+    std::cout << "\nTest 1- as std::vector<int>...";
+    std::vector<int> arr1 = {23, 10, 20, 11, 12, 6, 7};
+    sorting::pancake_sort::pancakeSort(arr1, size1);
+    assert(std::is_sorted(arr1.begin(), arr1.end()));
+    std::cout << "Passed\n";
+    for (int i = 0; i < size1; i++) {
+        std::cout << arr1[i] << " ,";
+    }
+    std::cout << std::endl;
+
+    // example 2: vector of double
+    const int size2 = 8;
+    std::cout << "\nTest 2- as std::vector<double>...";
+    std::vector<double> arr2 = {23.56, 10.62, 200.78, 111.484, 3.9, 1.2, 61.77, 79.6};
+    sorting::pancake_sort::pancakeSort(arr2, size2);
+    assert(std::is_sorted(arr2.begin(), arr2.end()));
+    std::cout << "Passed\n";
+    for (int i = 0; i < size2; i++) {
+        std::cout << arr2[i] << ", ";
+    }
+    std::cout << std::endl;
+
+    // example 3:vector of float
+    const int size3 = 7;
+    std::cout << "\nTest 3- as std::vector<float>...";
+    std::vector<float> arr3 = {6.56, 12.62, 200.78, 768.484, 19.27, 68.87, 9.6};
+    sorting::pancake_sort::pancakeSort(arr3, size3);
+    assert(std::is_sorted(arr3.begin(), arr3.end()));
+    std::cout << "Passed\n";
+    for (int i = 0; i < size3; i++) {
+        std::cout << arr3[i] << ", ";
+    }
+    std::cout << std::endl;
+}
+/**
+ * @brief Main function
+ * @returns 0 on exit
+ */
+int main() {
+    test();
+    return 0;
+}