poj 1503 Integer Inquiry

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

const int M = 100 + 10;
char input[M];
int A[M], sum[M];

void Reverse( int A[], const char str[] )
{
    int len = strlen( str );
    int index = 0;

    for ( int i = len - 1; i >= 0; --i )
        A[index++] = str[i] - ‘0‘;
}

int main()
{
    int sumLen = 0;

    memset( sum, 0, sizeof(sum) );
    while ( scanf( "%s", input ) != EOF )
    {
        int digitSum;

        if ( strcmp( input, "0") == 0 )
            break;

        memset( A, 0, sizeof(A) );
        Reverse( A, input );

        for ( int i = 0 ; i < M; ++i )
        {
            digitSum = sum[i] + A[i];
            sum[i] = digitSum % 10;
            sum[i+1] += digitSum/10;
        }
    }

    for ( int i = M-1; sum[i] == 0; --i )
        sumLen = i;

    for( int i = sumLen-1; i >= 0; --i )
        printf( "%d", sum[i] );
    printf( "\n" );

    return 0;
}