factorial-trailing-zeroes.md

172. Factorial Trailing Zeroes

Medium

---

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

Note that n! = n * (n - 1) * (n - 2) * ... * 3 * 2 * 1.

 

Example 1:

Input: n = 3
Output: 0
Explanation: 3! = 6, no trailing zero.

Example 2:

Input: n = 5
Output: 1
Explanation: 5! = 120, one trailing zero.

Example 3:

Input: n = 0
Output: 0

 

Constraints:

• 0 <= n <= 104

 

Follow up: Could you write a solution that works in logarithmic time complexity?

Solution:

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