quick.cpp

// C++ code to implement quicksort
 
#include <bits/stdc++.h>
using namespace std;
 
// This function takes last element as pivot,
// places the pivot element at its correct position
// in sorted array, and places all smaller to left
// of pivot and all greater elements to right of pivot
int partition(int arr[], int low, int high) {
    // Choosing the pivot
    int pivot = arr[high];
 
    // Index of smaller element and indicates
    // the right position of pivot found so far
    int i = (low - 1);
 
    for (int j = low; j <= high - 1; j++) {
 
        // If current element is smaller than the pivot
        if (arr[j] < pivot) {
 
            // Increment index of smaller element
            i++;
            swap(arr[i], arr[j]);
        }
    }
    swap(arr[i + 1], arr[high]);
    return (i + 1);
}
 
// The main function that implements QuickSort
// arr[] --> Array to be sorted,
// low --> Starting index,
// high --> Ending index
void quickSort(int arr[], int low, int high) {
    if (low < high) {
 
        // pi is partitioning index, arr[p]
        // is now at right place
        int pi = partition(arr, low, high);
 
        // Separately sort elements before
        // partition and after partition
        quickSort(arr, low, pi - 1);
        quickSort(arr, pi + 1, high);
    }
}
 
// Driver Code
int main() {
    int arr[] = { 10, 7, 8, 9, 1, 5 };
    int N = sizeof(arr) / sizeof(arr[0]);
 
    // Function call
    quickSort(arr, 0, N - 1);
    cout << "Sorted array: " << endl;
    for (int i = 0; i < N; i++)
        cout << arr[i] << " ";
    return 0;
}