<p>Given an integer array <code>nums</code>, return <em>the maximum result of </em><code>nums[i] XOR nums[j]</code>, where <code>0 &lt;= i &lt;= j &lt; n</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<pre>
<strong>Input:</strong> nums = [3,10,5,25,2,8]
<strong>Output:</strong> 28
<strong>Explanation:</strong> The maximum result is 5 XOR 25 = 28.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> nums = [14,70,53,83,49,91,36,80,92,51,66,70]
<strong>Output:</strong> 127
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= nums.length &lt;= 2 * 10<sup>5</sup></code></li>
	<li><code>0 &lt;= nums[i] &lt;= 2<sup>31</sup> - 1</code></li>
</ul>

class Solution {
public:
    class TrieNode {
    public:
        TrieNode* child[2];
        TrieNode() {
            child[0] = nullptr;
            child[1] = nullptr;
        }
    };

    class Trie {
    public:
        TrieNode* root;
        Trie() {
            root = new TrieNode();
        }

        void insert(vector<int>& arr) {
            TrieNode* node = root;
            for (int i = 0; i < arr.size(); i++) {
                int bit = arr[i];
                if (!node->child[bit]) {
                    node->child[bit] = new TrieNode();
                }
                node = node->child[bit];
            }
        }

        void search(vector<int>& arr, int& ans) {
            TrieNode* node = root;
            for (int i = 0; i < arr.size(); i++) {
                int bit = arr[i];
                if (node->child[!bit]) { // Opposite bit exists
                    ans = (ans << 1) | 1;
                    node = node->child[!bit];
                } else { // Follow the same bit
                    ans = (ans << 1);
                    node = node->child[bit];
                }
            }
        }
    };

    vector<int> dectobin(int num) {
        vector<int> ans(31);
        for (int i = 30; i >= 0; i--) {
            ans[30 - i] = (num >> i) & 1;
        }
        return ans;
    }

    int findMaximumXOR(vector<int>& nums) {
        Trie* t = new Trie();

        // Insert all numbers into the Trie in binary form
        for (int i = 0; i < nums.size(); i++) {
            vector<int> temp = dectobin(nums[i]);
            t->insert(temp);
        }

        int maxXor = 0;

        // Search for the maximum XOR
        for (int i = 0; i < nums.size(); i++) {
            vector<int> temp = dectobin(nums[i]);
            int currentXor = 0;
            t->search(temp, currentXor);
            maxXor = max(maxXor, currentXor);
        }

        return maxXor;
    }
};

398788