Sunday 13 August 2017

Merge Sort

#include<stdlib.h>
#include<stdio.h>
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 merge_Sort(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
        merge_Sort(arr, l, m);
        merge_Sort(arr, m+1, r);
 
        merge(arr, l, m, r);
    }
}
// Function to print an array
void print_Array(int A[], int size)
{
    int i;
    for (i=0; i < size; i++)
        printf("%d ", A[i]);
    printf("\n");
}

int main()
{
    int arr[] = {12, 11, 13, 5, 6, 7};
    int arr_size = sizeof(arr)/sizeof(arr[0]);
 
    printf("Given array is \n");
    print_Array(arr, arr_size);
 
    merge_Sort(arr, 0, arr_size - 1);
 
    printf("\nSorted array is \n");
    print_Array(arr, arr_size);
    return 0;
}

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