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| 1 | +/** |
| 2 | + * @file |
| 3 | + * @brief Insertion Sort Algorithm |
| 4 | + * @author [Dhanush S](https://github.com/Fandroid745) |
| 5 | + * |
| 6 | + * @details |
| 7 | + * Insertion sort is a simple sorting algorithm that builds the final |
| 8 | + * sorted array one element at a time. It is much less efficient compared |
| 9 | + * to other sorting algorithms like heap sort, merge sort, or quick sort. |
| 10 | + * |
| 11 | + * However, it has several advantages: |
| 12 | + * - Easy to implement. |
| 13 | + * - Efficient for small data sets. |
| 14 | + * - More efficient than other O(n2) algorithms like selection sort or bubble sort. |
| 15 | + * - Stable: it does not change the relative order of elements with equal keys. |
| 16 | + * |
| 17 | + * Insertion sort works similarly to how people sort playing cards in their hands. |
| 18 | + * The algorithm iterates through the list and inserts each element into its correct |
| 19 | + * position in the sorted portion of the array. |
| 20 | + * |
| 21 | + * The time complexity of the algorithm is \f$O(n^2)\f,ドル and in some cases, it |
| 22 | + * can be \f$O(n)\f$. |
| 23 | + * |
| 24 | + * Example execution: |
| 25 | + * 1. Start with the array [4, 3, 2, 5, 1]. |
| 26 | + * 2. Insert 3 in its correct position: [3, 4, 2, 5, 1]. |
| 27 | + * 3. Insert 2: [2, 3, 4, 5, 1]. |
| 28 | + * 4. Continue this until the array is sorted: [1, 2, 3, 4, 5]. |
| 29 | + */ |
| 30 | + |
| 31 | + |
| 32 | +#include <algorithm> /// for std::is_sorted |
| 33 | +#include <cassert> /// for assert function in testing |
| 34 | +#include <iostream> /// for std::cout and std::endl |
| 35 | +#include <vector> /// for using std::vector |
| 36 | + |
| 37 | +/** |
| 38 | + * @namespace sorting |
| 39 | + * @brief Contains sorting algorithms |
| 40 | + */ |
| 41 | +namespace sorting { |
| 42 | + |
| 43 | +/** |
| 44 | + * @brief Insertion Sort Function |
| 45 | + * |
| 46 | + * @tparam T Type of the array elements |
| 47 | + * @param[in,out] arr Array to be sorted |
| 48 | + * @param n Size of the array |
| 49 | + */ |
| 50 | +template <typename T> |
| 51 | +void insertionSort(T *arr, int n) { |
| 52 | + for (int i = 1; i < n; i++) { |
| 53 | + T temp = arr[i]; |
| 54 | + int j = i - 1; |
| 55 | + while (j >= 0 && temp < arr[j]) { |
| 56 | + arr[j + 1] = arr[j]; |
| 57 | + j--; |
| 58 | + } |
| 59 | + arr[j + 1] = temp; |
| 60 | + } |
| 61 | +} |
| 62 | + |
| 63 | +/** |
| 64 | + * @brief Insertion Sort for a vector |
| 65 | + * |
| 66 | + * @tparam T Type of the vector elements |
| 67 | + * @param [in,out] arr Pointer to the vector to be sorted |
| 68 | + */ |
| 69 | +template <typename T> |
| 70 | +void insertionSort(std::vector<T> *arr) { |
| 71 | + size_t n = arr->size(); |
| 72 | + |
| 73 | + for (size_t i = 1; i < n; i++) { |
| 74 | + T temp = arr->at(i); |
| 75 | + int32_t j = i - 1; |
| 76 | + while (j >= 0 && temp < arr->at(j)) { |
| 77 | + arr->at(j + 1) = arr->at(j); |
| 78 | + j--; |
| 79 | + } |
| 80 | + arr->at(j + 1) = temp; |
| 81 | + } |
| 82 | +} |
| 83 | + |
| 84 | +} // namespace sorting |
| 85 | + |
| 86 | +/** |
| 87 | + * @brief Helper function to create a random array |
| 88 | + * |
| 89 | + * @tparam T Type of the array elements |
| 90 | + * @param arr Array to fill (must be pre-allocated) |
| 91 | + * @param N Number of elements in the array |
| 92 | + */ |
| 93 | +template <typename T> |
| 94 | +static void create_random_array(T *arr, int N) { |
| 95 | + while (N--) { |
| 96 | + double r = (std::rand() % 10000 - 5000) / 100.f; |
| 97 | + arr[N] = static_cast<T>(r); |
| 98 | + } |
| 99 | +} |
| 100 | + |
| 101 | +/** |
| 102 | + * @brief self test implementation |
| 103 | + * @return void |
| 104 | + */ |
| 105 | +static void tests() { |
| 106 | + int arr1[10] = {78, 34, 35, 6, 34, 56, 3, 56, 2, 4}; |
| 107 | + std::cout << "Test 1... "; |
| 108 | + sorting::insertionSort(arr1, 10); |
| 109 | + assert(std::is_sorted(arr1, arr1 + 10)); |
| 110 | + std::cout << "passed" << std::endl; |
| 111 | + |
| 112 | + int arr2[5] = {5, -3, 7, -2, 1}; |
| 113 | + std::cout << "Test 2... "; |
| 114 | + sorting::insertionSort(arr2, 5); |
| 115 | + assert(std::is_sorted(arr2, arr2 + 5)); |
| 116 | + std::cout << "passed" << std::endl; |
| 117 | + |
| 118 | + float arr3[5] = {5.6, -3.1, -3.0, -2.1, 1.8}; |
| 119 | + std::cout << "Test 3... "; |
| 120 | + sorting::insertionSort(arr3, 5); |
| 121 | + assert(std::is_sorted(arr3, arr3 + 5)); |
| 122 | + std::cout << "passed" << std::endl; |
| 123 | + |
| 124 | + std::vector<float> arr4({5.6, -3.1, -3.0, -2.1, 1.8}); |
| 125 | + std::cout << "Test 4... "; |
| 126 | + sorting::insertionSort(&arr4); |
| 127 | + assert(std::is_sorted(std::begin(arr4), std::end(arr4))); |
| 128 | + std::cout << "passed" << std::endl; |
| 129 | + |
| 130 | + int arr5[50]; |
| 131 | + std::cout << "Test 5... "; |
| 132 | + create_random_array(arr5, 50); |
| 133 | + sorting::insertionSort(arr5, 50); |
| 134 | + assert(std::is_sorted(arr5, arr5 + 50)); |
| 135 | + std::cout << "passed" << std::endl; |
| 136 | + |
| 137 | + float arr6[50]; |
| 138 | + std::cout << "Test 6... "; |
| 139 | + create_random_array(arr6, 50); |
| 140 | + sorting::insertionSort(arr6, 50); |
| 141 | + assert(std::is_sorted(arr6, arr6 + 50)); |
| 142 | + std::cout << "passed" << std::endl; |
| 143 | +} |
| 144 | + |
| 145 | +/** |
| 146 | + * @brief Main function |
| 147 | + * @return 0 on successful exit. |
| 148 | + */ |
| 149 | +int main() { |
| 150 | + tests(); /// run self test implementations |
| 151 | + return 0; |
| 152 | +} |
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