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.

Hint:

1. 1. Beware of overflow.

1 int countDigitOne(int n) { 2     int count=0; 3     long m=1; 4     for(m=1;m<=n;m=m*10) 5     { 6         count+=(n/m+8)/10*m; 7         if(n/m%10==1) 8           count+=n%m+1; 9     }10     return count;11 }