LeetCode in Kotlin

421. Maximum XOR of Two Numbers in an Array

Medium

Given an integer array nums, return the maximum result of nums[i] XOR nums[j], where 0 <= i <= j < n.

Example 1:

Input: nums = [3,10,5,25,2,8]

Output: 28

Explanation: The maximum result is 5 XOR 25 = 28.

Example 2:

Input: nums = [14,70,53,83,49,91,36,80,92,51,66,70]

Output: 127

Constraints:

• 1 <= nums.length <= 2 * 105
• 0 <= nums[i] <= 231 - 1

Solution

class Solution {
    fun findMaximumXOR(nums: IntArray): Int {
        var max = 0
        var mask = 0
        val set: MutableSet<Int> = HashSet()
        var maxNum = 0
        for (i in nums) {
            maxNum = Math.max(maxNum, i)
        }
        for (i in 31 - Integer.numberOfLeadingZeros(maxNum) downTo 0) {
            set.clear()
            val bit = 1 shl i
            mask = mask or bit
            val temp = max or bit
            for (prefix in nums) {
                if (set.contains(prefix and mask xor temp)) {
                    max = temp
                    break
                }
                set.add(prefix and mask)
            }
        }
        return max
    }
}

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