C++ Exmaple 3

#include <iostream>
#include <vector>
#include <algorithm>
#include <chrono>

// Kaizer here. I implemented and compared different sorting algorithms using 3 main ones. quicksort, mergesort, and heapsort, in terms of performance.
// function to print an array
void printArray(const std::vector<int>& arr) {
    for (int num : arr) {
        std::cout << num << " ";
    }
    std::cout << std::endl;
}

// quicksort implementation
int partition(std::vector<int>& arr, int low, int high) {
    int pivot = arr[high];
    int i = low - 1;
    for (int j = low; j < high; j++) {
        if (arr[j] < pivot) {
            i++;
            std::swap(arr[i], arr[j]);
        }
    }
    std::swap(arr[i + 1], arr[high]);
    return i + 1;
}

void quicksort(std::vector<int>& arr, int low, int high) {
    if (low < high) {
        int pi = partition(arr, low, high);
        quicksort(arr, low, pi - 1);
        quicksort(arr, pi + 1, high);
    }
}

// mergesort implementation
void merge(std::vector<int>& arr, int left, int mid, int right) {
    int n1 = mid - left + 1;
    int n2 = right - mid;
    std::vector<int> L(n1), R(n2);

    for (int i = 0; i < n1; i++)
        L[i] = arr[left + i];
    for (int j = 0; j < n2; j++)
        R[j] = arr[mid + 1 + j];

    int i = 0, j = 0, k = left;
    while (i < n1 && j < n2) {
        if (L[i] <= R[j]) {
            arr[k] = L[i];
            i++;
        } else {
            arr[k] = R[j];
            j++;
        }
        k++;
    }

    while (i < n1) {
        arr[k] = L[i];
        i++;
        k++;
    }

    while (j < n2) {
        arr[k] = R[j];
        j++;
        k++;
    }
}

void mergesort(std::vector<int>& arr, int left, int right) {
    if (left < right) {
        int mid = left + (right - left) / 2;
        mergesort(arr, left, mid);
        mergesort(arr, mid + 1, right);
        merge(arr, left, mid, right);
    }
}

// heapsort implementation
void heapify(std::vector<int>& arr, int n, int i) {
    int largest = i;
    int left = 2 * i + 1;
    int right = 2 * i + 2;

    if (left < n && arr[left] > arr[largest])
        largest = left;

    if (right < n && arr[right] > arr[largest])
        largest = right;

    if (largest != i) {
        std::swap(arr[i], arr[largest]);
        heapify(arr, n, largest);
    }
}

void heapsort(std::vector<int>& arr) {
    int n = arr.size();
    for (int i = n / 2 - 1; i >= 0; i--)
        heapify(arr, n, i);

    for (int i = n - 1; i > 0; i--) {
        std::swap(arr[0], arr[i]);
        heapify(arr, i, 0);
    }
}

// function to measure and compare sorting times
void compareSorts(std::vector<int> arr) {
    std::vector<int> arr1 = arr;
    std::vector<int> arr2 = arr;
    std::vector<int> arr3 = arr;

    auto start = std::chrono::high_resolution_clock::now();
    quicksort(arr1, 0, arr1.size() - 1);
    auto end = std::chrono::high_resolution_clock::now();
    std::chrono::duration<double> quicksortTime = end - start;
    std::cout << "Quicksort time: " << quicksortTime.count() << " seconds" << std::endl;

    start = std::chrono::high_resolution_clock::now();
    mergesort(arr2, 0, arr2.size() - 1);
    end = std::chrono::high_resolution_clock::now();
    std::chrono::duration<double> mergesortTime = end - start;
    std::cout << "Mergesort time: " << mergesortTime.count() << " seconds" << std::endl;

    start = std::chrono::high_resolution_clock::now();
    heapsort(arr3);
    end = std::chrono::high_resolution_clock::now();
    std::chrono::duration<double> heapsortTime = end - start;
    std::cout << "Heapsort time: " << heapsortTime.count() << " seconds" << std::endl;
}

int main() {
    std::vector<int> arr = {12, 11, 13, 5, 6, 7};
    std::cout << "Original array: ";
    printArray(arr);

    compareSorts(arr);

    return 0;
}