By | 27.11.2016

# Merge Sort using Recursion

Write a C Program to implement Merge Sort using Recursion. Here’s simple Program to implement Merge Sort using Recursion in C Programming Language.

## Recursion : :

• Recursion is the process of repeating items in a self-similar way. In programming languages, if a program allows you to call a function inside the same function, then it is called a recursive call of the function.
• The C programming language supports recursion, i.e., a function to call itself. But while using recursion, programmers need to be careful to define an exit condition from the function, otherwise it will go into an infinite loop.
• Recursive functions are very useful to solve many mathematical problems, such as calculating the factorial of a number, generating Fibonacci series, etc.

## Problem : :

The following C program, using recursion, performs merge sort. A merge sort is a sorting algorithm with complexity of O(nlogn). It is used for sorting numbers, structure, files.

Here is the source code of the C Program to implement Merge Sort using Recursion. The C Program is successfully compiled and run on a Windows system. The program output is also shown below.

### SOURCE CODE : :

```/*  C Program to implement Merge Sort using Recursion  */

#include <stdio.h>

void mergeSort(int [], int, int, int);
void partition(int [],int, int);

int main()
{
int list[50];
int i, size;

printf("How Many elements u want to Sort :: ");
scanf("%d", &size);

printf("\nEnter [ %d ] elements below to be Sorted :: \n",size);

for(i = 0; i < size; i++)
{
printf("\nEnter [ %d ] Element :: ",i+1);
scanf("%d", &list[i]);
}

partition(list, 0, size - 1);

printf("\n\nAfter implementing Merge sort, Sorted List is :: \n\n");
for(i = 0;i < size; i++)
{
printf("%d   ",list[i]);
}

printf("\n");

return 0;
}

void partition(int list[],int low,int high)
{
int mid;

if(low < high)
{
mid = (low + high) / 2;
partition(list, low, mid);
partition(list, mid + 1, high);
mergeSort(list, low, mid, high);
}
}

void mergeSort(int list[],int low,int mid,int high)
{
int i, mi, k, lo, temp[50];

lo = low;
i = low;
mi = mid + 1;
while ((lo <= mid) && (mi <= high))
{
if (list[lo] <= list[mi])
{
temp[i] = list[lo];
lo++;
}
else
{
temp[i] = list[mi];
mi++;
}
i++;
}
if (lo > mid)
{
for (k = mi; k <= high; k++)
{
temp[i] = list[k];
i++;
}
}
else
{
for (k = lo; k <= mid; k++)
{
temp[i] = list[k];
i++;
}
}

for (k = low; k <= high; k++)
{
list[k] = temp[k];
}
}```

### Output : :

```/*  C Program to implement Merge Sort using Recursion  */

How Many elements u want to Sort :: 8

Enter [ 8 ] elements below to be Sorted ::

Enter [ 1 ] Element :: 4

Enter [ 2 ] Element :: 1

Enter [ 3 ] Element :: 3

Enter [ 4 ] Element :: 2

Enter [ 5 ] Element :: 5

Enter [ 6 ] Element :: 8

Enter [ 7 ] Element :: 6

Enter [ 8 ] Element :: 9

After implementing Merge sort, Sorted List is ::

1   2   3   4   5   6   8   9

Process returned 0```

Above is the source code for C Program to implement Merge Sort using Recursion which is successfully compiled and run on Windows System.The Output of the program is shown above .

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