Ackermann's function (recursive)

ack.cpp

#include <bits/stdc++.h>
using namespace std;
int ack(int m, int n){
    int ans;
    if( m == 0 ) ans = n + 1;
    else if( n == 0 ) ans = ack(m - 1, 1);
    else ans = ack(m - 1, ack(m, n-1));    
    return (ans);
}
int main(){
    printf( "ack(%d, %d) is %d\n", 4, 0, ack(4,0) );
}