//https://leetcode.com/problems/number-of-digit-one/
Given an integer n, count the total number of digit 1 appearing in all non-negative integers less than or equal to n.
For example:
Given n = 13,
Return 6, because digit 1 occurred in the following numbers: 1, 10, 11, 12, 13.
class Solution {
public:
int countDigitOne(int n) {
int ones = ;
for (long long m = ; m <= n; m *= )
ones += (n/m + ) / * m + (n/m % == ) * (n%m + );
return ones;
}
};