3644 - Maximum K to Sort a Permutation.

Medium

You are given an integer array nums of length n, where nums is a permutation of the numbers in the range [0..n - 1].

You may swap elements at indices i and j only if nums[i] AND nums[j] == k, where AND denotes the bitwise AND operation and k is a non-negative integer.

Return the maximum value of k such that the array can be sorted in non-decreasing order using any number of such swaps. If nums is already sorted, return 0.

A permutation is a rearrangement of all the elements of an array.

Example 1:

Input: nums = 0,3,2,1

Output: 1

Explanation:

Choose k = 1. Swapping nums[1] = 3 and nums[3] = 1 is allowed since nums[1] AND nums[3] == 1, resulting in a sorted permutation: [0, 1, 2, 3].

Example 2:

Input: nums = 0,1,3,2

Output: 2

Explanation:

Choose k = 2. Swapping nums[2] = 3 and nums[3] = 2 is allowed since nums[2] AND nums[3] == 2, resulting in a sorted permutation: [0, 1, 2, 3].

Example 3:

Input: nums = 3,2,1,0

Output: 0

Explanation:

Only k = 0 allows sorting since no greater k allows the required swaps where nums[i] AND nums[j] == k.

Constraints:

• <code>1 <= n == nums.length <= 10⁵</code>

• 0 <= nums[i] <= n - 1

• nums is a permutation of integers from 0 to n - 1.