Kyselyt

#include <iostream>
#include <vector>
#include <math.h>
#include <string>

using namespace std;

uint64_t mod(uint64_t x, uint64_t y) {
	return x - y * (x / y);
}

vector<uint64_t> getIndexes() {
	uint64_t count, num;
    vector<uint64_t> indexes;
    cin >> count;

    for (uint64_t i = 0; i < count; ++i)
    {
    	cin >> num;
    	indexes.push_back(num);
    }
    return indexes;
}

uint64_t f(uint64_t x) {
	return 9 * x * pow(10, x-1);
}

uint64_t getFirstNumber(uint64_t index, uint64_t numCount) {
	return floor(index / (numCount * pow(10, numCount-1))) + 1;
}

uint64_t getMiddleNumber(uint64_t index, uint64_t numCount, uint64_t subNumber) {
	uint64_t j = floor(floor(index / numCount) / pow(10, numCount - subNumber));
	return mod(j, 10);
}

uint64_t getLastNumber(uint64_t index, uint64_t numCount) {
	return mod(((index / numCount) - 1), 10);
}

uint64_t getNumberFromIndex(uint64_t index) {
	if (index <= 9)
		return index;

	uint64_t numCount = 1;
	while (index > f(numCount)) {
		index -= f(numCount);
		numCount++;
	}
	switch (uint64_t subNumber = mod(index, numCount)){
		case 0:
			return getLastNumber(index, numCount);
			break;
		case 1:
			return getFirstNumber(index, numCount);
			break;
		default:
			return getMiddleNumber(index, numCount, subNumber);
			break;
	}
}

void test(uint64_t n) {
	string right, guess;
	for (unsigned i=1; i<n; i++)
    	guess += to_string(getNumberFromIndex(i));
    for (unsigned i=1; i<n; i++)
    	right += to_string(i);
    right = right.substr(0, n-1);
    if (right.compare(guess) == 0)
    	cout << "Right!";
   	else
   		cout << right << '\n' << guess << '\n';
}

void real() {
	auto indexes = getIndexes();
    for (unsigned i=0; i<indexes.size(); i++)
    	cout << getNumberFromIndex(indexes.at(i)) << '\n';
}

int main() {
	//test(pow(10, 9));
	real();
    return 0;
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED

Test 3

Group: 3

Verdict: WRONG ANSWER