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Given an integer n, count the total number of digit 1 appearing in all non-negative integers less than or equal to n.

 

Example 1:

Input: n = 13
Output: 6

Example 2:

Input: n = 0
Output: 0

 

Constraints:

  • 0 <= n <= 2 * 109

class Solution { public int countDigitOne(int n) { } }