# LeetCode 172. Factorial Trailing Zeroes

2021年4月8日 11:29 · Updated at 2021年4月23日 17:41

## 172. Factorial Trailing Zeroes

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

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

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
```

## Solve

JavaScript solution with short (hard to read🤣) code

### Code

1 | var trailingZeroes = function (n) { |

### Explain

As we know, `0`

only apear when multiply has `5`

and `5`

‘s multiple, and below every `5`

‘s multiple, there will always has an even which can multiply `5`

‘s multiple be a `0`

end number.

so I just need find out how many `5`

‘s multiple exsist in given number `N`

Last! Also as all we know, `25`

is double `5`

, which can make a `two 0`

end number, and so on

So, just count how many `5`

in `N`

and plus how many `5*5`

in `N`

and `5*5*5`

in `N`

….

*Note: number | 0 is a shot way to get trunc Int number but it requires number less than (2^31)-1*