C++ straight-forward solution with explanation

  • 0
    class Solution {
        int findNthDigit(int n) {
            int i = 0;
                int minus = i*(pow(10,i)-pow(10,i-1));
                if(n-minus>0) n-=minus;
                else break;
            int res = (n+i-1)/i+pow(10,i-1)-1;
            string result = to_string(res);
            return result[(n+i-1)%i]-'0';
    • we divided numbers into several parts:
      1~9 10~99 100~999 ...
    • first, we determine which part the result belongs to.
      the i in the while loop means the ith part.
    • then we find the number that the digit belongs to,
      which is res in the code.
    • finally we find the position of the digit in the number.

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