How hard is LeetCode 172. Factorial Trailing Zeroes?

LeetCode 172. Factorial Trailing Zeroes is rated Medium on LeetCode.

What is the time complexity of LeetCode 172. Factorial Trailing Zeroes?

The Python solution on this page runs in O(\log n).

What is the space complexity of LeetCode 172. Factorial Trailing Zeroes?

The Python solution on this page uses O(1) auxiliary space.

What topics does LeetCode 172. Factorial Trailing Zeroes cover?

LeetCode 172. Factorial Trailing Zeroes is tagged Math on LeetCode.

Factorial Trailing Zeroes — LeetCode 172 Python Solution

MediumMath

Problem: #172
Pattern: Math and Number Theory
Reading time: 2 min
Source: leetcode.com

The problem

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

Example

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

Python solution

Python

class Solution:
    def trailingZeroes(self, n: int) -> int:
        ans = 0
        while n:
            n //= 5
            ans += n
        return ans

Complexity

Measure	Complexity
Time	O(\log n)
Space	O(1) auxiliary

Pattern: Math and Number Theory

Find the closed form, the invariant, or the modular identity — and skip the loop entirely. LeetCode 172. Factorial Trailing Zeroes is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Math.

The math and number theory guide has the Python template for the pattern and the 485 LeetCode problems that use it.

On a study list

This problem is on Top Interview 150.

Frequently asked questions

How hard is LeetCode 172. Factorial Trailing Zeroes?: LeetCode 172. Factorial Trailing Zeroes is rated Medium on LeetCode.
What is the time complexity of LeetCode 172. Factorial Trailing Zeroes?: The Python solution on this page runs in O(\log n).
What is the space complexity of LeetCode 172. Factorial Trailing Zeroes?: The Python solution on this page uses O(1) auxiliary space.
What topics does LeetCode 172. Factorial Trailing Zeroes cover?: LeetCode 172. Factorial Trailing Zeroes is tagged Math on LeetCode.