HDU : 2714 (ISBN)



// http://acm.hdu.edu.cn/showproblem.php?pid=2714
// Runtime: 0ms
// Tag: Adhoc

/* 
 * File:   main.cpp
 * Author: shahab
 * Created on March 18, 2011, 5:05 PM
 */

// @BEGIN_OF_SOURCE_CODE

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <string>
#include <cctype>
#include <stack>
#include <queue>
#include <list>
#include <vector>
#include <map>
#include <sstream>
#include <cmath>
#include <bitset>
#include <utility>
#include <set>
#include <numeric>

#define INF_MAX 2147483647
#define INF_MIN -2147483647
#define pi acos(-1.0)
#define N 1000000
#define LL long long

#define For(i, a, b) for ( int i = (a); i < (b); i++ )
#define Fors(i, sz) for ( size_t i = 0; i < sz.size (); i++ )
#define Set(a, s) memset (a, s, sizeof (a))

using namespace std;

char a [20];

void findVal (int pos)
{
    a [pos] = '0';
    int sum = 0;

    for ( int i = 0; i < 10; i++ ) {
        if ( a [i] >= '0' && a [i] <= '9' ) sum += (10 - i) * (a [i] - '0');
        else sum += (10 - i) * 10;
    }

    for ( int i = 0; i < 10; i++ ) {
        if ( (sum + (10 - pos) * i) % 11 == 0 ) {
            printf ("%c\n", '0' + i);
            return;
        }
    }

    if ( pos != 9 ) { printf ("-1\n"); return; }
    if ( (sum + 10) % 11 == 0 ) printf ("X\n");
    else printf ("-1\n");
}

int main(int argc, char** argv) {
    
    while ( scanf ("%s", a) == 1 ) {
        for ( int i = 0; i < 10; i++ ) {
            if ( a [i] == '?' ) {
                findVal (i);
                break;
            }
        }
    }
    return 0;
}

// @END_OF_SOURCE_CODE

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