PROBLEM:
Find the nth digit of the infinite integer sequence 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, ...
Note:
n is positive and will fit within the range of a 32-bit signed integer (n < 231).
Example 1:
Input: 3 Output: 3
Example 2:
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.
SOLVE:
class Solution { public: int findNthDigit(int n) { int len=1; //the length of the number int start=1; //the first number of different length long long count=9; //number of digits before 'start' while(n>count*len){ n-=count*len; len++; start*=10; count*=10; } start+=(n-1)/len; string res=to_string(start); return res[(n-1)%len]-'0'; } };