172 Factorial Trailing Zeroes

Given an integer n, return the number of trailing zeroes in n!.

Note: Your solution should be in logarithmic time complexity.

找规律

http://www.geeksforgeeks.org/count-trailing-zeroes-factorial-number/

http://blog.youkuaiyun.com/doc_sgl/article/details/42344441

class Solution {
public:
    int trailingZeroes(int n) {
        int ans = 0;
        while(n)
        {
            ans += n / 5;
            n /= 5;
        }
        return ans;
    }
};