Kyselyt

import java.util.*;
/*
 * Datatähti 2018
 * Tuomas Karjalainen, Nurmeksen lukio
 */
public class Kyselyt {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    int queries = Integer.parseInt(input.nextLine());
    while (queries-- > 0) {
      long k = Long.parseLong(input.nextLine());
      System.out.println(query(k));
    }
  }

  private static char query(long k) {
    long index = 1;
    long currentNumber = 1;
    long numberLength, numberCountWithLength;
    while ((numberLength = numberLength(currentNumber)) != 0 &&
          (numberCountWithLength = numberCountWithLength(numberLength)) != 0 &&
          (index + numberCountWithLength * numberLength) <= k) {
      index += numberCountWithLength * numberLength;
      currentNumber += numberCountWithLength;
    }
    long diff = (k - index);
    index += diff - diff % numberLength(currentNumber);
    currentNumber += diff / (long) numberLength(currentNumber);
    return Long.toString(currentNumber).charAt((int)(k - index));
  }

  private static long numberLength(long number) {
    long length = 0;
    while (number > 0) {
      number /= 10;
      length++;
    }
    return length;
  }

  private static long numberCountWithLength(long length) {
    return 9 * (long) Math.pow(10, length - 1);
  }
}

Test 1

Group: 1

Verdict: ACCEPTED

Test 2

Group: 2

Verdict: ACCEPTED

Test 3

Group: 3

Verdict: ACCEPTED