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/**
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* @file
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* @brief Implementation of [Saddleback Algorithm](https://www.geeksforgeeks.org/saddleback-search-algorithm-in-a-2d-array) for 2D arrays.
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* @brief Implementation of [Saddleback
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* Algorithm](https://www.geeksforgeeks.org/saddleback-search-algorithm-in-a-2d-array)
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* for 2D arrays.
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*
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* @details
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* Saddleback Algorithm is an algorithm that searches 2D array in linear time,
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* i.e, O(m + n), where m is number of rows and n is number of columns of 2D array. Also, each row and
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* column of the matrix should be sorted beforehand for this algorithm to work.
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* i.e, O(m + n), where m is number of rows and n is number of columns of 2D
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* array. Also, each row and column of the matrix should be sorted beforehand
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* for this algorithm to work.
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*
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* @author [Hashir Niazi](https://github.com/HashirGJ8842)
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*/
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#include <cassert> /// for assert
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#include <iostream> /// for io operations, and std::pair
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#include <vector> /// for std::vector
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#include <cassert> /// for assert
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#include <cstdint> /// for integral typedefs
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#include <iostream> /// for io operations, and std::pair
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#include <vector> /// for std::vector
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/** \namespace search
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* \brief Algorithms for searching
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*/
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namespace search {
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/** \namespace saddleback
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* \brief Function for implementing [Saddleback Algorithm](https://www.geeksforgeeks.org/saddleback-search-algorithm-in-a-2d-array).
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* \brief Function for implementing [Saddleback
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* Algorithm](https://www.geeksforgeeks.org/saddleback-search-algorithm-in-a-2d-array).
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*/
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namespace saddleback {
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/**
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* This function implements [Saddleback Algorithm](https://www.geeksforgeeks.org/saddleback-search-algorithm-in-a-2d-array),
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* This function implements [Saddleback
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* Algorithm](https://www.geeksforgeeks.org/saddleback-search-algorithm-in-a-2d-array),
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* on a sorted 2D array, and finds the location of the element needed to search
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* @param matrix 2D matrix which is sorted on the basis of rows and columns
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* @param element element to be searched
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@@ -30,16 +36,17 @@ namespace saddleback {
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* element is present.
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* @return An std::pair with (0, 0), if the element is not present.
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*/
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std::pair<uint32_t, uint32_t> saddleback(std::vector<std::vector<int32_t>> matrix,
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int32_t element) {
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std::pair<uint32_t, uint32_t> saddleback(
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std::vector<std::vector<int32_t>> matrix, int32_t element) {
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uint32_t left_index = 0;
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uint32_t right_index = matrix[0].size() - 1; // Start from top right corner
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while (left_index < matrix.size()) { // Exit once the value of indexes get out of range.
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while (left_index <
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matrix.size()) { // Exit once the value of indexes get out of range.
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if (element ==
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matrix[left_index]
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[right_index]) { // If value on this position of matrix is
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// equal to element, return (row, column).
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return std::make_pair(left_index+1, right_index+1);
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return std::make_pair(left_index + 1, right_index + 1);
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} else if (element >
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matrix[left_index]
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[right_index]) { // Else if value on this position of
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@@ -51,14 +58,15 @@ std::pair<uint32_t, uint32_t> saddleback(std::vector<std::vector<int32_t>> matri
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[right_index]) { // Else if value on this position of
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// matrix is greater than the
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// element, move down.
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if(!right_index)
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if (!right_index)
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break;
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else --right_index;
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else
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--right_index;
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}
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}
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return std::make_pair(
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0, 0); // If the program reaches here, that means one of the index
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// went out of index, hence no element present.
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// went out of index, hence no element present.
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}
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} // namespace saddleback
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} // namespace search
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@@ -69,15 +77,16 @@ std::pair<uint32_t, uint32_t> saddleback(std::vector<std::vector<int32_t>> matri
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*/
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static void test() {
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std::vector<std::vector<int32_t>> matrix = {{1, 10, 100, 1000, 10000},
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{2, 20, 200, 2000, 20000},
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{3, 30, 300, 3000, 30000},
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{4, 40, 400, 4000, 40000},
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{5, 50, 500, 5000, 50000}};
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{2, 20, 200, 2000, 20000},
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{3, 30, 300, 3000, 30000},
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{4, 40, 400, 4000, 40000},
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{5, 50, 500, 5000, 50000}};
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std::pair<uint32_t, uint32_t> not_found = std::make_pair(0, 0);
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std::pair<uint32_t, uint32_t> test_answer;
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// Test 1
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std::pair<uint32_t, uint32_t> answer1 = search::saddleback::saddleback(matrix, 123);
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std::pair<uint32_t, uint32_t> answer1 =
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search::saddleback::saddleback(matrix, 123);
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assert(not_found == answer1);
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// Test 2
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answer1 = search::saddleback::saddleback(matrix, 0);
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@@ -101,6 +110,6 @@ static void test() {
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* @returns 0 on exit
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*/
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int main() {
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test(); // execute the tests
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test(); // execute the tests
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return 0;
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}
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