Merge Sort

CODE

Merge Sort

/* C program for Merge Sort */

#include<stdlib.h>

#include<stdio.h>

// Merges two subarrays of arr[].

// First subarray is arr[l..m]

// Second subarray is arr[m+1..r]

void merge(int arr[], int l, int m, int r)

{

    int i, j, k;

    int n1 = m - l + 1;

    int n2 =  r - m;

    /* create temp arrays */

    int L[n1], R[n2];

    /* Copy data to temp arrays L[] and R[] */

    for (i = 0; i < n1; i++)

        L[i] = arr[l + i];

    for (j = 0; j < n2; j++)

        R[j] = arr[m + 1+ j];

    /* Merge the temp arrays back into arr[l..r]*/

    i = 0; // Initial index of first subarray

    j = 0; // Initial index of second subarray

    k = l; // Initial index of merged subarray

    while (i < n1 && j < n2)

    {

        if (L[i] <= R[j])

        {

            arr[k] = L[i];

            i++;

        }

        else

        {

            arr[k] = R[j];

            j++;

        }

      k++;

    }

    /* Copy the remaining elements of L[], if there are any */

    while (i < n1)

    {

        arr[k] = L[i];

        i++;

        k++;

    }  

    /* Copy the remaining elements of R[], if there are any */

    while (j < n2)

    {

        arr[k] = R[j];

        j++;

        k++;

    }

}

/* l is for left index and r is right index of the sub-array of arr to be sorted */

void mergeSort(int arr[], int l, int r)

{

    if (l < r)

    {

        // Same as (l+r)/2, but avoids overflow for

        // large l and h

        int m = l+(r-l)/2;

        // Sort first and second halves

        mergeSort(arr, l, m);

        mergeSort(arr, m+1, r);

  merge(arr, l, m, r);

    }

}

/* UTILITY FUNCTIONS */

/* Function to print an array */

void printArray(int A[], int size)

{

    int i;

    for (i=0; i < size; i++)

        printf("%d ", A[i]);

    printf("\n");

} 

/* Driver program to test above functions */

int main()

{

    int arr[] = {12, 11, 13, 5, 6, 7};

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

    printf("Given array is \n");

    printArray(arr, arr_size);

    mergeSort(arr, 0, arr_size - 1);

    printf("\nSorted array is \n");

    printArray(arr, arr_size);

    return 0;

}

Output:

Given array is

12 11 13 5 6 7

Sorted array is

5 6 7 11 12 13