LeetCode-in-Java
400. Nth Digit
Medium
Given an integer n, return the nth digit of the infinite integer sequence [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ...].
Example 1:
Input: n = 3
Output: 3
Example 2:
Input: n = 11
Output: 0
Explanation: The 11th digit of the sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, … is a 0, which is part of the number 10.
Constraints:
1 <= n <= 231 - 1
Solution
public class Solution {
/*
* 1. find the length of the number where the nth digit is from
* 2. find the actual number where the nth digit is from
* 3. find the nth digit and return
*/
public int findNthDigit(int n) {
int len = 1;
long count = 9;
int start = 1;
while (n > len * count) {
n -= (int) (len * count);
len += 1;
count *= 10;
start *= 10;
}
start += (n - 1) / len;
String s = Integer.toString(start);
return Character.getNumericValue(s.charAt((n - 1) % len));
}
}