C++ Quick sort Exercise: Sort a collection of integers using the Quick sort

Last update on August 20 2025 12:35:58 (UTC/GMT +8 hours)

12. Sort a Collection Using the Quick Sort Algorithm

Write a C++ program to sort a collection of integers using Quick sort.

Sample Solution:

C++ Code :

#include <iostream>

// Function to perform quick sort
void quick_Sort(int *nums, int low, int high) {
    // Initializing indices and pivot
    int i = low;
    int j = high;
    int pivot = nums[(i + j) / 2];
    int temp;

    // Partitioning step of the quicksort algorithm
    while (i <= j) {
        // Finding elements less than the pivot on the left side
        while (nums[i] < pivot)
            i++;

        // Finding elements greater than the pivot on the right side
        while (nums[j] > pivot)
            j--;

        // Swapping elements to maintain order
        if (i <= j) {
            temp = nums[i];
            nums[i] = nums[j];
            nums[j] = temp;
            i++;
            j--;
        }
    }

    // Recursive calls for the remaining partitions
    if (j > low)
        quick_Sort(nums, low, j);
    if (i < high)
        quick_Sort(nums, i, high);
}

// Main function
int main() {
    // Initializing an array of integers for sorting
    int nums[] = {125, 0, 695, 3, -256, -5, 214, 44, 55};

    // Calculating the number of elements in the array
    int n = sizeof(nums) / sizeof(nums[0]);

    // Displaying the original numbers in the array
    std::cout << "Before Quick Sort:" << std::endl;
    for (int i = 0; i < n; ++i)
        std::cout << nums[i] << " ";

    // Calling the quicksort function
    quick_Sort(nums, 0, n - 1);

    // Displaying the sorted numbers after Quick Sort
    std::cout << "\nAfter Quick Sort:" << std::endl;
    for (int i = 0; i < n; ++i)
        std::cout << nums[i] << " ";

    return (0);
}

Sample Output:

Before Quick Sort:
125 0 695 3 -256 -5 214 44 55 
After Quick Sort:
-256 -5 0 3 44 55 125 214 695

Flowchart:

For more Practice: Solve these Related Problems:

Write a C++ program to implement quick sort with randomized pivot selection and print pivot choices.
Write a C++ program to implement quick sort using the Lomuto partition scheme and count recursive calls.
Write a C++ program to implement quick sort and handle duplicate pivot elements gracefully.
Write a C++ program to implement quick sort and display each partitioning step during the recursion.

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