Find thenthdigit of the infinite integer sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ...
Input: 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.
class Solution {
public int findNthDigit(int n) {
// 记录target number的长度
int digits = 1;
// 这里要用Long防止overflow
long count = 9;
int startNum = 1;
// Step 1: 找到第n个 digit所在的数的长度
while (n > count * digits) {
n -= count * digits;
digits += 1;
count *= 10;
startNum *= 10;
}
// Step 2:找到target number
int target = start + (n - 1) / digits; //减一是因为start本身算一个数
String s = Integer.toString(target); // 将target转成字符串方便下一步找到nth digit
// Step 3: (n - 1) % digits是nth digit在target number的位置
return Character.getNumericValue(s.charAt((n - 1) % digits));
}
}