leetcode-go/leetcode/easy/400.nth-digit.go

func findNthDigit(n int) int {
	nines, digits := 9, 1
	for nines*digits < n {
		n -= nines * digits
		nines *= 10
		digits++
	}
	num := nines/9 + (n-1)/digits
	for i := 0; i < digits-(n-1)%digits-1; i++ {
		num /= 10
	}
	return num % 10
}