What is the error in this mergesort program in C??

Question

// Online C compiler to run C program online
#include <stdio.h>
void mergesort();
void merge();

int main()
{ int n,i;
printf("enter size of array");
scanf("%d",&n);
int a[n];
printf("enter elements");
for(i=0;i<n;i++);
scanf("%d",&a[i]);
mergesort(a,0,n-1);
}

void mergesort(int a[],int first,int last)
{ int mid;
if(first<last)
{
mid=(first+last)/2;
mergesort(a,first,mid);
mergesort(a,mid+1,last);
merge(a,first,mid,last);

}
}
void merge(int a[],int first,int mid,int last)
{
int b[50];
int i,j,k;
i=first,j=mid+1,k=first;
while(i<=mid&&j<=last)
{
if(a[i]<=a[j])
{
b[k]=a[i];
k++,i++;}
else{
b[k]=a[j];
k++,j++;
}
} if(i>mid)
{while(j<=last)
b[k]=a[j];
k++,j++;}
else
{
while(i<=mid)
b[k]=a[i];
k++,i++;
}

for(i=first;i<=last;i++)
a[i]=b[i];

printf("sorted elements");
int n;
for(i=0;i< n;i++)
printf("%d",a[i]);
}

Answer 1

You have mismatching function prototypes..

You have semicolon after a loop in main, remove it.

And some of missing, mismatching braces {, } in merge function. Check again..
And
Last 4 lines should be put in main at last instead of in merge() function. In that remove int n; declaration. It is Unitialized there and initialized in main.

Try these changes and it works...
Hope it helps...