3845. Maximum Subarray XOR with Bounded Range

You are given a non-negative integer array nums and an integer k.

You must select a subarray of nums such that the difference between its maximum and minimum elements is at most k. The value of this subarray is the bitwise XOR of all elements in the subarray.

Return an integer denoting the maximum possible value of the selected subarray.

3863. Minimum Operations to Sort a String

You are given a string s consisting of lowercase English letters.

In one operation, you can select any substring of s that is not the entire string and sort it in non-descending alphabetical order.

Return the minimum number of operations required to make s sorted in non-descending order. If it is not possible, return -1.

3848. Check Digitorial Permutation

You are given an integer n.

A number is called digitorial if the sum of the factorials of its digits is equal to the number itself.

Determine whether any permutation of n (including the original order) forms a digitorial number.

Return true if such a permutation exists, otherwise return false.

Note:

• The factorial of a non-negative integer x, denoted as x!, is the product of all positive integers less than or equal to x, and 0! = 1.
• A permutation is a rearrangement of all the digits of a number that does not start with zero. Any arrangement starting with zero is invalid.

3850. Count Sequences to K

You are given an integer array nums, and an integer k.

Start with an initial value val = 1 and process nums from left to right. At each index i, you must choose exactly one of the following actions:

• Multiply val by nums[i].
• Divide val by nums[i].
• Leave val unchanged.

After processing all elements, val is considered equal to k only if its final rational value exactly equals k.

Return the count of distinct sequences of choices that result in val == k.

Note: Division is rational (exact), not integer division. For example, 2 / 4 = 1 / 2.

3849. Maximum Bitwise XOR After Rearrangement

You are given two binary strings s and t​​​​​​​, each of length n.

You may rearrange the characters of t in any order, but s must remain unchanged.

Return a binary string of length n representing the maximum integer value obtainable by taking the bitwise XOR of s and rearranged t.

3852. Smallest Pair With Different Frequencies

You are given an integer array nums.

Consider all pairs of distinct values x and y from nums such that:

• x < y
• x and y have different frequencies in nums.

Among all such pairs:

• Choose the pair with the smallest possible value of x.
• If multiple pairs have the same x, choose the one with the smallest possible value of y.

Return an integer array [x, y]. If no valid pair exists, return [-1, -1].

3870. Count Commas in Range

You are given an integer n.

Return the total number of commas used when writing all integers from [1, n] (inclusive) in standard number formatting.

In standard formatting:

• A comma is inserted after every three digits from the right.
• Numbers with fewer than 4 digits contain no commas.

3869. Count Fancy Numbers in a Range

You are given two integers l and r.

An integer is called good if its digits form a strictly monotone sequence, meaning the digits are strictly increasing or strictly decreasing. All single-digit integers are considered good.

An integer is called fancy if it is good, or if the sum of its digits is good.

Return an integer representing the number of fancy integers in the range [l, r] (inclusive).

A sequence is said to be strictly increasing if each element is strictly greater than its previous one (if exists).

A sequence is said to be strictly decreasing if each element is strictly less than its previous one (if exists).

3866. First Unique Even Element

You are given an integer array nums.

Return an integer denoting the first even integer (earliest by array index) that appears exactly once in nums. If no such integer exists, return -1.

An integer x is considered even if it is divisible by 2.

3868. Minimum Cost to Equalize Arrays Using Swaps

You are given two integer arrays nums1 and nums2 of size n.

You can perform the following two operations any number of times on these two arrays:

• Swap within the same array: Choose two indices i and j. Then, choose either to swap nums1[i] and nums1[j], or nums2[i] and nums2[j]. This operation is free of charge.
• Swap between two arrays: Choose an index i. Then, swap nums1[i] and nums2[i]. This operation incurs a cost of 1.

Return an integer denoting the minimum cost to make nums1 and nums2 identical. If this is not possible, return -1.