I need a implementation of IN PLACE MERGE SORT in C language

I need a implementation of IN PLACE MERGE SORT, in C++ language, that will work on an array of numbers.

Solution

Answer:-

Merge Sort :

MergeSort is a Divide and Conquer algorithm. It divides input array in two halves, calls itself for the two halves and then merges the two sorted halves. The merge() function is used for merging two halves. The merge(arr, l, m, r) is key process that assumes that arr[l..m] and arr[m+1..r] are sorted and merges the two sorted sub-arrays into one.

#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(\"\ \");
}

/* 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 \ \");
   printArray(arr, arr_size);

   mergeSort(arr, 0, arr_size - 1);

   printf(\"\ Sorted array is \ \");
   printArray(arr, arr_size);
   return 0;
}