0421-maximum-xor-of-two-numbers-in-an-array.js

/**
 * 421. Maximum XOR of Two Numbers in an Array
 * https://leetcode.com/problems/maximum-xor-of-two-numbers-in-an-array/
 * Difficulty: Medium
 *
 * Given an integer array nums, return the maximum result of nums[i] XOR
 * nums[j], where 0 <= i <= j < n.
 */

/**
 * @param {number[]} nums
 * @return {number}
 */
var findMaximumXOR = function(nums) {
  let result = 0;

  for (let i = 31, mask = 0; i >= 0; i--) {
    mask |= (1 << i);
    const set = new Set(nums.map(num => num & mask));
    const target = result | (1 << i);
    for (const prefix of set) {
      if (set.has(prefix ^ target)) {
        result = target;
        break;
      }
    }
  }

  return result;
};