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.

题意：求n的阶乘结果里会有多少个0

思路：这个问题跟5有关，找跟5有关的个数。

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