merge sort for practical file

#include<iostream.h>
#include<conio.h>
#include<time.h>
void mergesort(int [],int,int);
void merge(int[],int,int,int);
void main()
{
int a[10],p,q,r,i,n;
clrscr();
clock_t start,end;
cout<<"enter the number of elements";
cin>>n;
start=clock();
p=0;
r=n-1;
cout<<"enter the array";
for(i=0;i<n;i++)
{
cin>>a[i];
}
mergesort(a,p,r);
end=clock();
cout<<"the sorted array is";
for(i=0;i<n;i++)
{
cout<<"\n"<<a[i];
}
cout<<""the time complexity is"<<(end-start)/CLK_TCK;
getch();
}
void mergesort(int a[],int p,int r)
{
if(p<r)
{
int q=(p+r)/2;
mergesort(a,p,q);
mergesort(a,q+1,r) ;
merge(a,p,q,r);
}
}
void merge(int a[],int p,int q,int r)
{
int c[10];
int i=p;
int j=q+1;
int k=p;
while((i<=q)&&(j<=r))
{
if(a[i]<a[j])
{
c[k] =a[i];
i=i+1;
k=k+1;
}
else
{
c[k]=a[j];
j=j+1;
k=k+1;
}
}
while(i<=q)
{
c[k]=a[i];
i=i+1;
k=k+1;
}
while(j<=r)
{
c[k]=a[j];
j=j+1;
k=k+1;
}
int l=p;
while(l<=r)
{
a[l]=c[l];
l=l+1;
}
}