LeetCode in Kotlin

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 11^th 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

@Suppress("NAME_SHADOWING")
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
     */
    fun findNthDigit(n: Int): Int {
        var n = n
        var len = 1
        var count: Long = 9
        var start = 1
        while (n > len * count) {
            n -= (len * count).toInt()
            len += 1
            count *= 10
            start *= 10
        }
        start += (n - 1) / len
        val s = Integer.toString(start)
        return Character.getNumericValue(s[(n - 1) % len])
    }
}

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