How to write code for the quicksort algorithm in C++?

12 months ago

Liam

2 minutes

#include <iostream>
#include <vector>

void quickSort(std::vector<int>& arr, int low, int high) {
    if (low < high) {
        int pivot = arr[low];
        int i = low + 1;
        int j = high;

        while (i <= j) {
            if (arr[i] <= pivot) {
                i++;
            } else if (arr[j] > pivot) {
                j--;
            } else {
                std::swap(arr[i], arr[j]);
            }
        }

        std::swap(arr[low], arr[j]);

        quickSort(arr, low, j - 1);
        quickSort(arr, j + 1, high);
    }
}

int main() {
    std::vector<int> arr = {5, 2, 9, 3, 7, 1, 8, 4, 6};
    quickSort(arr, 0, arr.size() - 1);

    std::cout << "Sorted array: ";
    for (int num : arr) {
        std::cout << num << " ";
    }
    std::cout << std::endl;

    return 0;
}

This code implements the quick sort algorithm to sort an array of integers. It recursively divides the array into two parts, sorts each part, and finally obtains a sorted array. In the main function, we define an integer array and call the quickSort function to sort it, then output the sorted result.