<p>You are given an array <code>nums</code> consisting of non-negative integers. You are also given a <code>queries</code> array, where <code>queries[i] = [x<sub>i</sub>, m<sub>i</sub>]</code>.</p>

<p>The answer to the <code>i<sup>th</sup></code> query is the maximum bitwise <code>XOR</code> value of <code>x<sub>i</sub></code> and any element of <code>nums</code> that does not exceed <code>m<sub>i</sub></code>. In other words, the answer is <code>max(nums[j] XOR x<sub>i</sub>)</code> for all <code>j</code> such that <code>nums[j] &lt;= m<sub>i</sub></code>. If all elements in <code>nums</code> are larger than <code>m<sub>i</sub></code>, then the answer is <code>-1</code>.</p>

<p>Return <em>an integer array </em><code>answer</code><em> where </em><code>answer.length == queries.length</code><em> and </em><code>answer[i]</code><em> is the answer to the </em><code>i<sup>th</sup></code><em> query.</em></p>

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

<pre>
<strong>Input:</strong> nums = [0,1,2,3,4], queries = [[3,1],[1,3],[5,6]]
<strong>Output:</strong> [3,3,7]
<strong>Explanation:</strong>
1) 0 and 1 are the only two integers not greater than 1. 0 XOR 3 = 3 and 1 XOR 3 = 2. The larger of the two is 3.
2) 1 XOR 2 = 3.
3) 5 XOR 2 = 7.
</pre>

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

<pre>
<strong>Input:</strong> nums = [5,2,4,6,6,3], queries = [[12,4],[8,1],[6,3]]
<strong>Output:</strong> [15,-1,5]
</pre>

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

<ul>
	<li><code>1 &lt;= nums.length, queries.length &lt;= 10<sup>5</sup></code></li>
	<li><code>queries[i].length == 2</code></li>
	<li><code>0 &lt;= nums[j], x<sub>i</sub>, m<sub>i</sub> &lt;= 10<sup>9</sup></code></li>
</ul>

class TrieNode {
private:
    vector<TrieNode*> links;
    int flag;
public:
    TrieNode ()
    {
        links.resize(2, NULL);
        flag = -1;
    }

    bool containsKey(int bit)
    {
        return links[bit] != NULL;
    }

    void put(int bit, TrieNode* node)
    {
        links[bit] = node;
    }

    TrieNode* get(int bit)
    {
        return links[bit];
    }

    void setEnd(int val)
    {
        flag = val;
    }
    
    int getEnd()
    {
        return flag;
    }
};

class Trie {
private:
    TrieNode* root;
    int count;
public:

    Trie() {
        root = new TrieNode();
        count = 0;
    }
    
    void insert(int num) {
        
        TrieNode* temp = root;
        int bit = 0;;
        for(int i=31 ; i>=0 ; i--)
        {
            bit = (num >> i) & 1;
            if(!temp->containsKey(bit)) { temp->put(bit, new TrieNode()); }
            temp = temp->get(bit);
        }   
        temp->setEnd(num);
        count += 1;
    }

    int maxXOR(int num)
    {
        if(count == 0) return -1;
        TrieNode* temp = root;
        int bit = 0;
        for(int i=31 ; i >= 0 ; i--)
        {
            bit = (num >> i) & 1;
            if(temp->containsKey(bit ^ 1))
            {
                temp = temp->get(bit ^ 1);
            }else
            {
                temp = temp->get(bit);
            }
        } 
        return num ^ temp->getEnd();
    }

};

class Solution {
public:
    
    vector<int> maximizeXor(vector<int>& nums, vector<vector<int>>& q) {
        
        int n = nums.size(), m = q.size(), i = 0;
        vector<pair<int, pair<int, int>>> mp(m);
        vector<int> ans(m, 0);
        for(int i=0 ; i<m ; i++)
        {
            mp[i] = {q[i][1], {q[i][0], i}};
        }        
        
        sort(nums.begin(), nums.end());
        sort(mp.begin(), mp.end());

        Trie t;
        i = 0;

        for(auto &m: mp)
        {
            while(i < n && nums[i] <= m.first)
            {
                t.insert(nums[i]);
                i += 1;
            }
            ans[m.second.second] = t.maxXOR(m.second.first);
        }
        return ans;
    }
};
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