String to Integer using Recursion.

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
#define siz 10
char as[siz];

int string_to_int(char as[], int len, int i, int sum){
    if(i == len) return sum;
    sum = sum*10 + (as[i] - '0');
    string_to_int(as, len, i+1, sum);
}

int main()
{
    while(gets(as)){
        int len = strlen(as);
        cout<<string_to_int(as, len, 0, 0)<<endl;
    }
    return 0;
}