# Next Integer Permutation

Given an integer `n`

, return the next bigger permutation of its digits.

If `n`

is already in its biggest permutation, rotate to the smallest permutation.

**Constraints**

`n < 2 ** 31`

https://binarysearch.com/problems/Next-Integer-Permutation

## Examples

### Example 1

**Input**

- n =
`321`

**Output**

- answer =
`123`

**Explanation**

321 is already the biggest permutation so it rotates to the smallest.

### Example 2

**Input**

- n =
`527`

**Output**

- answer =
`572`

### Example 3

**Input**

- n =
`20`

**Output**

- answer =
`2`

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