数字以0123456789101112131415…的格式序列化到一个字符序列中。在这个序列中，第5位（从下标0开始计数）是5，第13位是1，第19位是4，等等。
请写一个函数，求任意第n位对应的数字。
示例 1：
输入：n = 3
输出：3示例 2：
输入：n = 11
输出：0限制：
0 <= n < 2^31
//leetcode submit region begin(Prohibit modification and deletion)
class Solution {
public int findNthDigit(int n) {
int low = 1, high = 9;
while (low < high) {
int mid = (high - low) / 2 + low;
if (totalDigits(mid) < n) {
low = mid + 1;
} else {
high = mid;
}
}
int d = low;
int prevDigits = totalDigits(d - 1);
int index = n - prevDigits - 1;
int start = (int) Math.pow(10, d - 1);
int num = start + index / d;
int digitIndex = index % d;
int digit = (num / (int) (Math.pow(10, d - digitIndex - 1))) % 10;
return digit;
}
public int totalDigits(int length) {
int digits = 0;
int curLength = 1, curCount = 9;
while (curLength <= length) {
digits += curLength * curCount;
curLength++;
curCount *= 10;
}
return digits;
}
}
//leetcode submit region end(Prohibit modification and deletion)
