Quick Sort
Quick Sort Algorithm in C++ (Complete Implementation)
IntermediateTopic: Sorting & Searching Programs
C++ Quick Sort Program
This program helps you to learn the fundamental structure and syntax of C++ programming.
#include <iostream>
using namespace std;
int partition(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++;
swap(arr[i], arr[j]);
}
}
swap(arr[i + 1], arr[high]);
return i + 1;
}
void quickSort(int arr[], int low, int high) {
if (low < high) {
int pi = partition(arr, low, high);
// Recursively sort elements before and after partition
quickSort(arr, low, pi - 1);
quickSort(arr, pi + 1, high);
}
}
void printArray(int arr[], int n) {
for (int i = 0; i < n; i++) {
cout << arr[i] << " ";
}
cout << endl;
}
int main() {
int arr[] = {64, 34, 25, 12, 22, 11, 90};
int n = sizeof(arr) / sizeof(arr[0]);
cout << "Original array: ";
printArray(arr, n);
quickSort(arr, 0, n - 1);
cout << "Sorted array: ";
printArray(arr, n);
return 0;
}Output
Original array: 64 34 25 12 22 11 90 Sorted array: 11 12 22 25 34 64 90
Understanding Quick Sort
Quick Sort is a divide-and-conquer algorithm that picks a pivot element and partitions the array around it. Time Complexity: O(n log n) average, O(n²) worst case. Space Complexity: O(log n). It's not stable but is in-place and generally faster than Merge Sort in practice.
Note: To write and run C++ programs, you need to set up the local environment on your computer. Refer to the complete article Setting up C++ Development Environment. If you do not want to set up the local environment on your computer, you can also use online IDE to write and run your C++ programs.