Merge sort not showing correct output - c

Question

I have implemented each line of merge sort algorithm-wise and can't find error.
al and ar are left and right sub arrays. Arrays are passed along with size.
#include<stdio.h>
#include<conio.h>
void mergesort(int a[] ,int);
void merge(int al[],int,int ar[],int,int a[]);
int main()
{
int i,n;
printf("Enter the no of elements to be sorted\n");
scanf("%d",&n);
int a[n];
for(i=0;i<n;i++)
{
scanf("%d",&a[i]);
}
mergesort(a,n);
printf("\nThe elements after sorting are:");
for(i=0;i<n;i++)
{
printf("%d ",a[i]);
}
getch();
return 0;
}
void mergesort(int a[],int size)
{
int i,n=size,mid;
if(n<2)
return;
mid=n/2;
int left[mid],right[n-mid];
for(i=0;i<mid;i++)
left[i]=a[i];
for(i=mid;i<n;i++)
right[i]=a[i];
mergesort(left,mid);
mergesort(right,n-mid);
merge(left,mid,right,n-mid,a);
}
void merge(int al[],int sl,int ar[],int sr,int a[])
{
int i=0,j=0,k=0;
while(i<sl && j<sr)
{
if(al[i]<=ar[j])
{
a[k]=al[i];
i++;
}
else
{
a[k]=ar[j];
j++;
}
k++;
}
while(i<sl)
{
a[k]=al[i];
i++;
k++;
}
while(j<sr)
{
a[k]=ar[j];
j++;
k++;
}
}
input:
no of elements:4
5 6 3 1
output:
5 16 16 16

Answer 1

Look at this part of your code:
int left[mid],right[n-mid];
for(i=0;i<mid;i++)
left[i]=a[i];
for(i=mid;i<n;i++)
right[i]=a[i];
You are accessing the right array with indexes beyond the array bounds. That should be something like this instead:
right[i - mid]=a[i];

Answer 2

I have correct code for merge sort written in C. Please tally with it.
#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);
mergesort(a,mid+1,j);
merge(a,i,mid,mid+1,j);
}
}
void merge(int a[],int i1,int j1,int i2,int j2)
{
int temp[50];
int i,j,k;
i=i1;
j=i2;
k=0;
while(i<=j1 && j <=j2)
{
if(a[i]<a[j])
temp[k++]=a[i++];
else
temp[k++]=a[j++];
}
while(i<=j1)
temp[k++]=a[i++];
while(j<=j2)
temp[k++]=a[j++];
for(i=i1,j=0;i<=j2;i++,j++)
a[i]=temp[j];
}