# 1053. Previous Permutation With One Swap

https://leetcode.com/problems/previous-permutation-with-one-swap

## Description

Given an array of positive integers `arr` (not necessarily distinct), return _the lexicographically largest permutation that is smaller than_ `arr`, that can be **made with exactly one swap** (A _swap_ exchanges the positions of two numbers `arr[i]` and `arr[j]`). If it cannot be done, then return the same array.

**Example 1:**

```
**Input:** arr = [3,2,1]
**Output:** [3,1,2]
**Explanation:** Swapping 2 and 1.
```

**Example 2:**

```
**Input:** arr = [1,1,5]
**Output:** [1,1,5]
**Explanation:** This is already the smallest permutation.
```

**Example 3:**

```
**Input:** arr = [1,9,4,6,7]
**Output:** [1,7,4,6,9]
**Explanation:** Swapping 9 and 7.
```

**Example 4:**

```
**Input:** arr = [3,1,1,3]
**Output:** [1,3,1,3]
**Explanation:** Swapping 1 and 3.
```

**Constraints:**

* `1 <= arr.length <= 104`
* `1 <= arr[i] <= 104`

## ac

```java
```
