# LeetCode - 0172. Factorial Trailing Zeroes
### 題目網址：https://leetcode.com/problems/factorial-trailing-zeroes/
###### tags: `LeetCode` `Easy` `數學`

/*
    -LeetCode format-
    Problem: 172. Factorial Trailing Zeroes
    Difficulty: Easy
    
    by Inversionpeter
*/



class Solution {
public:
    int trailingZeroes(int n) {
        const int upperBound = (INT_MAX / 5);
        int fives = 0, base = 5;
        while (base <= n) {
            fives += n / base;
            if (base > upperBound)
                break;
            base = (base << 2) + base;
        }
        return fives;
    }
};