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.

Constraints:

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