class Node {
public:
    Node* lists[2];
    bool final = false;
    
    bool containsKey(int c) {
        return lists[c] != nullptr;
    }
};

class Trie {
public:
    Node* root;
    Trie() {
        root = new Node();
    }
    
    void insert(int num) {
        Node* node = root;
        for(int i = 31; i >= 0; i--) {
            int c = ((num & (1 << i)) != 0);
            if(!node->containsKey(c)) {
                node->lists[c] = new Node();
            }
            node = node->lists[c];
        }
        node->final = true;
    }
    
    int invert(int c) {
        return ((c == 1) ? 0 : 1);
    }
    
    int maxXOR(vector<int>& nums) {
        Node* node = root;
        int num = 0, ans = 0;
        for(auto n : nums) {
            num = 0;
            node = root;
            for(int i = 31; i >= 0; i--) {
                int c = ((n & (1 << i)) != 0);
                if(node->containsKey(invert(c))) {
                    num = num | (1 << i);
                    node = node->lists[invert(c)];
                }
                else{
                    node = node->lists[c];
                }
            }
            if(num > ans) ans = num;
        }
        return ans;
    }
};
class Solution {
public:
    int findMaximumXOR(vector<int>& nums) {
        Trie* trie = new Trie();
        for(auto num : nums) {
            trie->insert(num);
        }
        return trie->maxXOR(nums);
    }
};