Code giving Run Time Error for the problem Maximum XOR pair in a given Range

Question

I am trying to solve a well known problem called the Maximum XOR pair ina given range. If you are unaware about the probelm here is the prompt given to me:

You are given an array and Q queries of two types.
Type 0: Given a number x , insert the number at the last of the array.
Type 1: Given a number X and two integers L, R, Find a number Y in the range L, R to maximize X ^ Y

Input Format
First line of the test case will be the number of queries Q . Then on next Q subsequent lines you will be given a query either of type 0 or type 1. Query of type 0 is of the form : 0 X, where X is the integer to be inserted . Query of type 1 is of the form : 1 L R X

Constraints
0 <= element of array <= 10^9
1 <= N <= 10^5

Output Format
For each query of type 1 output the desired value.

Sample Input
5
0 3 
0 5
0 10 
0 6 
1 1 4 6
Sample Output
10

I am using Tries to find out the maximum XOR for the given question my for some reason it gives a Run Time Error in 2 test cases. I am not sure why is that. Please help!

Here is my code:

#include<bits/stdc++.h>

using namespace std;

class node {
public:
    int index;
    node * left; // data = 0
    node * right; // data = 1
};

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

    void insert(int n, int idx) {
        // ith bit of a number is (n >> i) & 1
        node * temp = root;
        for(int i = 31; i >= 0; i--) {
            int bit = (n >> i) & 1;
            if(bit == 0) {
                if(temp->left == NULL) {
                    temp->left = new node();
                    temp->index = idx;
                }
                temp = temp->left;
            }
            else {
                if(temp->right == NULL) {
                    temp->right = new node();
                    temp->index = idx;
                }

                temp = temp->right;
            }
        }
    }

    int max_xor_helper(long long int value, int L, int R) {
        node * temp = root;
        long long int current_ans = 0;
        for(int j = 31; j >= 0; j--) {
            int bit = (value >> j) & 1;
            if(bit == 0) {
                // finding complimentary value
                if(temp->right != NULL and temp->index >= L and temp->index <= R) {
                    temp = temp->right;
                    current_ans += (1 << j); // 2 ^ j
                }
                else {
                    temp = temp->left;
                }
            }
            else {
                if(temp->left != NULL and temp->index >= L and temp->index <= R) {
                    temp = temp->left;
                }
                else {
                    temp = temp->right;
                    current_ans += (1 << j);
                }
            }
        }

        return current_ans;
    }
};


int maxXORPair(Trie root, int L, int R, int X) {
    // Trie root;
    // int max_xor = 0, max_xor_partner = 0;
    // for(int i = L; i <= R; i++) {
    //  int val = arr[i];
    //  root.insert(val);
    //  int curr_ans = root.max_xor_helper(X, L, R);
    //  if(curr_ans > max_xor) {
    //      max_xor_partner = curr_ans ^ val;
    //      max_xor = curr_ans;
    //  }
    // }

    return root.max_xor_helper(X, L, R);
}

int main() {
    Trie root;
    int idx = 0;
    // vector<int> v;
    int queries;
    cin>>queries;
    for(int i = 0; i < queries; i++) {
        int type;
        cin>>type;
        if(type == 0) {
            long long int val;
            cin>>val;
            root.insert(val, idx);
            idx++;
            // v.push_back(val);
        }
        else {
            int L, R;
            cin>>L>>R;
            long long int X;
            cin>>X;

            long int ans = maxXORPair(root, L, R, X);
            cout<<ans<<endl;
        }
    }
    return 0;
}

Answer 1

See: https://www.learncpp.com/cpp-tutorial/null-pointers

Just like normal variables, pointers are not initialized when they are instantiated.

Initialize your pointers to NULL.