Submission #112040

#	Time	Username	Problem	Language	Result	Execution time	Memory
112040		fredbr	Lun (COCI19_lun)	C++17	50 / 50	2 ms	384 KiB

lun

#include <bits/stdc++.h>

using namespace std;

bool valid(string const& s) {
    auto f = [](int x) {
        if (x >= 10) return x/10+x%10;
        return x;
    };

    int acc = 0;
    for (int i = (int)s.size()-2; i >= 0; i--) {
        int x = s[i]-'0';

        if ((s.size()-1-i)&1) acc += f(2*x);
        else acc += x;
    }

    acc = acc*9%10;

    return acc == s.back()-'0';
}

int main() {
    int n;
    cin >> n;

    string s;
    cin >> s;

    int xpos = 0;
    for (int i = 0; i < n; i++) {
        if (s[i] >= '0' and s[i] <= '9') continue;
        xpos = i;
    }

    for (int i = '0'; i <= '9'; i++) {
        s[xpos] = i;
        if (valid(s)) {
            cout << char(i) << "\n";
            return 0;
        }
    }

}

• Subtask 1: 50 / 50