### Write a C Program for MergeSort

```  #include <stdio.h>
void mergesort(int a[],int i,int j);
void merge(int a[],int i1,int j1,int i2,int j2);

int main()
{
int a[30],n,i;
printf("Enter no of elements:");
scanf("%d",&n);
printf("Enter array elements:");

for(i=0;i<n;i++)
scanf("%d",&a[i]);

mergesort(a,0,n-1);

printf("\nSorted array is :");
for(i=0;i<n;i++)
printf("%d ",a[i]);

return 0;
}
void mergesort(int a[],int i,int j)
{
int mid;

if(i<j)
{
mid=(i+j)/2;
mergesort(a,i,mid);		//left recursion
mergesort(a,mid+1,j);	//right recursion
merge(a,i,mid,mid+1,j);	//merging of two sorted sub-arrays
}
}

void merge(int a[],int i1,int j1,int i2,int j2)
{
int temp[50];	//array used for merging
int i,j,k;
i=i1;	//beginning of the first list
j=i2;	//beginning of the second list
k=0;

while(i<=j1 && j<=j2)	//while elements in both lists
{
if(a[i]<a[j])
temp[k++]=a[i++];
else
temp[k++]=a[j++];
}

while(i<=j1)	//copy remaining elements of the first list
temp[k++]=a[i++];

while(j<=j2)	//copy remaining elements of the second list
temp[k++]=a[j++];

//Transfer elements from temp[] back to a[]
for(i=i1,j=0;i<=j2;i++,j++)
a[i]=temp[j];
}
```

### Output:

``` Enter no of elements:6
Enter array elements:12
15
25
36
64
0

Sorted array is :0 12 15 25 36 64
--------------------------------
```