Quick Sort

Download Quick Sort

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//

//  main.cpp

//  Quick_Sort

//

//  Created by Zhenlin Pei on 12/24/18.

//  Copyright © 2018 Zhenlin Pei. All rights reserved.

//

/* C implementation QuickSort */

#include<stdio.h>

// A utility function to swap two elements

void swap(int* a, int* b)

{

    int t = *a;

    *a = *b;

    *b = t;

}

/* This function takes last element as pivot, places

 the pivot element at its correct position in sorted

 array, and places all smaller (smaller than pivot)

 to left of pivot and all greater elements to right

 of pivot */

int partition (int arr[], int low, int high)

{

    int pivot = arr[high]; // pivot

    int i = (low – 1); // Index of smaller element

    

    for (int j = low; j <= high- 1; j++)

    {

        // If current element is smaller than or

        // equal to pivot

        if (arr[j] <= pivot)

        {

            i++; // increment index of smaller element

            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);

    }

}

/* Function to print an array */

void printArray(int arr[], int size)

{

    int i;

    for (i=0; i < size; i++)

        printf(“%d “, arr[i]);

    printf(“\n”);

}

// Driver program to test above functions

int main()

{

    int arr[] = {10, 7, 8, 9, 1, 5};

    int n = sizeof(arr)/sizeof(arr[0]);

    quickSort(arr, 0, n-1);

    printf(“Sorted array: \n”);

    printArray(arr, n);

    return 0;

}

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