L6MaxXorQueriesJava

import java.util.ArrayList;
import java.util.*; 
class Node {
    Node links[] = new Node[2]; 
    
    public Node() {
    }
    boolean containsKey(int ind) {
        return (links[ind] != null); 
    }
    Node get(int ind) {
        return links[ind]; 
    }
    void put(int ind, Node node) {
        links[ind] = node; 
    }
};
class Trie {
    private static Node root; 

    //Initialize your data structure here

    Trie() {
        root = new Node(); 
    }


    //Inserts a word into the trie

    public static void insert(int num) {
        Node node = root;
        for(int i = 31;i>=0;i--) {
            int bit = (num >> i) & 1; 
            if(!node.containsKey(bit)) {
                node.put(bit, new Node()); 
            }
            node = node.get(bit); 
        }
    }
    
    public int getMax(int num) {
        Node node = root; 
        int maxNum = 0; 
        for(int i = 31;i>=0;i--) {
            int bit = (num >> i) & 1; 
            if(node.containsKey(1 - bit)) {
                maxNum = maxNum | (1<<i);
                node = node.get( 1 - bit); 
            }
            else {
                node = node.get(bit); 
            }
        }
        return maxNum; 
    }
};
public class Solution {
    public static ArrayList<Integer> maxXorQueries(ArrayList<Integer> arr, ArrayList<ArrayList<Integer>> queries) {
         Collections.sort(arr); 
         ArrayList<ArrayList<Integer>> offlineQueries = new ArrayList<ArrayList<Integer>>(); 
         int m = queries.size(); 
         for(int i = 0;i<m;i++) {
             ArrayList<Integer> temp = new ArrayList<Integer>(); 
             temp.add(queries.get(i).get(1)); 
             temp.add(queries.get(i).get(0)); 
             temp.add(i); 
             offlineQueries.add(temp); 
         }
         Collections.sort(offlineQueries, new Comparator<ArrayList<Integer>> () {
            @Override
            public int compare(ArrayList<Integer> a, ArrayList<Integer> b) {
                return a.get(0).compareTo(b.get(0));
            }
        });
         int ind = 0;
         int n = arr.size(); 
         Trie trie = new Trie(); 
         ArrayList<Integer> ans = new ArrayList<Integer>(m); 
         for(int i = 0;i<m;i++) ans.add(-1); 
         for(int i = 0;i<m;i++) {
             while(ind<n && arr.get(ind) <= offlineQueries.get(i).get(0)) {
                 trie.insert(arr.get(ind)); 
                 ind++; 
             }
             int queryInd = offlineQueries.get(i).get(2); 
             if(ind!=0) ans.set(queryInd, trie.getMax(offlineQueries.get(i).get(1)));
             else ans.set(queryInd, -1); 
         }
         return ans; 
    }
}