TheAlgorithms-C-Plus-Plus/sorting/gnome_sort.cpp

/**
 * @file
 * @brief Implementation of [gnome
 * sort](https://en.wikipedia.org/wiki/Gnome_sort) algorithm.
 * @author [beqakd](https://github.com/beqakd)
 * @author [Krishna Vedala](https://github.com/kvedala)
 * @details
 * Gnome sort algorithm is not the best one but it is widely used.
 * The algorithm iteratively checks the order of pairs in the array. If they are
 * on right order it moves to the next successive pair, otherwise it swaps
 * elements. This operation is repeated until no more swaps are made thus
 * indicating the values to be in ascending order.
 *
 * The time Complexity of the algorithm is \f$O(n^2)\f$ and in some cases it
 * can be \f$O(n)\f$.
 */

#include <algorithm>  // for std::swap
#include <array>      // for std::array
#include <iostream>   // for io operations

/**
 * @namespace sorting
 * Sorting algorithms
 */
namespace sorting {
/**
 * This implementation is for a C-style array input that gets modified in place.
 * @param [in,out] arr our array of elements.
 * @param size size of given array
 */
template <typename T>
void gnomeSort(T *arr, int size) {
    // few easy cases
    if (size <= 1) return;

    int index = 0;  // initialize some variables.
    while (index < size) {
        // check for swap
        if ((index == 0) || (arr[index] >= arr[index - 1])) {
            index++;
        } else {
            std::swap(arr[index], arr[index - 1]);  // swap
            index--;
        }
    }
}

/**
 * This implementation is for a C++-style array input. The function is a
 * pass-by-value and hence a copy of the array gets created which is then
 * modified by the function and returned.
 * @tparam T type of data variables in the array
 * @tparam size size of the array
 * @param [in] arr our array of elements.
 * @return array with elements sorted
 */
template <typename T, size_t size>
std::array<T, size> gnomeSort(std::array<T, size> arr) {
    // few easy cases
    if (size <= 1) return;

    int index = 1;  // initialize loop index
    while (index < size) {
        // check for swap
        if (arr[index] >= arr[index - 1]) {
            index++;
        } else {
            std::swap(arr[index], arr[index - 1]);  // swap
            index--;
        }
    }
    return arr;
}
}  // namespace sorting

/**
 * Test function
 */
static void test() {
    // Example 1. Creating array of int,
    std::cout << "Test 1 - as a C-array...";
    int size = 6;
    std::array<int, size> arr = {-22, 100, 150, 35, -10, 99};
    sorting::gnomeSort(arr.data, size);
    // for (int i = 0; i < size; i++) std::cout << arr[i] << " ";

    std::cout << "\n" << std::endl;

    // Example 2. Creating array of doubles.
    std::array<double, size> double_arr = {-100.2, 10.2, 20.0, 9.0, 7.5, 7.2};
    std::array<double, size> sorted_arr = sorting::gnomeSort(double_arr);
    for (int i = 0; i < size; i++) std::cout << double_arr[i] << " ";
}

/**
 * Our main function with example of sort method.
 */
int main() {
    test();
    return 0;
}