Mergesort

#include<cstdio>
#include<iostream>
using namespace std;

void Merge( int a[], int first, int mid, int last ) {
int b[1000], e;
int i = first;
int j = mid + 1;
int len = last - first + 1;
for( e = 0; e < len; e++ ) {
if( i == mid + 1 ) b[e] = a[j++];
else if( j == last +1 ) b[e] = a[i++];
else if( a[i] < a[j] ) b[e] = a[i++];
else b[e] = a[j++];
}
for( int k = 0; k < len; k++ ) {
a[first + k] = b[k];
}
}

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

int main()
{
int n;
while( cin >> n ) {
int a[1000];
for( int i = 0; i < n; i++ ) {
cin >> a[i];
}
Mergesort( a, 0, n - 1 );
for( int i = 0; i < n; i++) {
cout << a[i] << ' ';
}
cout << endl;
}
return 0;
}