题目：

题解：

func findNthDigit(n int) int {
    d := 1
    for count := 9; n > d*count; count *= 10 {
        n -= d * count
        d++
    }
    index := n - 1
    start := int(math.Pow10(d - 1))
    num := start + index/d
    digitIndex := index % d
    return num / int(math.Pow10(d-digitIndex-1)) % 10
}