Kyselyt

#include <iostream>
#include <string>
#include <cmath>
#include <vector>
//#include <set>

using namespace std;

//typedef unsigned long ul;
typedef unsigned long long ull;

ull cms(int mag) { //calculate magnitude size
    ull c = 0;
    for (int i = 1; i <= mag; i++) {
        c += (pow(10, i) - pow(10, i -1)) * i;
    }
    return c;
}

int get_mag(ull n) {
    ull c = 0;
    int i = 1;
    while (c < n) {
        c += (pow(10, i) - pow(10, i - 1)) * i;
        i += 1;
    }
    return i - 1;
}

char locate_digit(ull n) {
    int mag = get_mag(n);
    n -= cms(mag - 1);
    ull i = pow(10, mag - 1) + ceil((float)n / (float)mag) - 1;
    string str = to_string(i);
    //cout << " | n: " << n%mag << " | i: " << i << " | ans: " << str[(n+1) % mag] << endl;
    return str[(n+1) % mag];
}

int main(int argc, const char * argv[]) {
    /*for (int i = 1; i <= 1000; i++) {
        locate_digit(i);
        //cout << locate_digit(i) << endl;
    }*/
    int num;
    ull x;
    cin >> num;
    vector <ull> vec = {};
    for (int i = 0; i < num; i++) {
        cin >> x;
        vec.push_back(x);
    }
    for (int i = 0; i < num; i++) {
        cout << locate_digit(vec[i]) - '0' << endl;
    }
    return 0;
}

Test 1

Group: 1

Verdict: WRONG ANSWER

Test 2

Group: 2

Verdict: WRONG ANSWER

Test 3

Group: 3

Verdict: WRONG ANSWER