main.cpp

#include <iostream>
using namespace std;

struct TreeNode {
    int val;
    TreeNode *left;
    TreeNode *right;
    TreeNode(int x): val(x), left(NULL), right(NULL) {}
};

class BinarySearchTree {
public:
    TreeNode *root;

    BinarySearchTree() : root(NULL) {}

    TreeNode* insert(TreeNode* root, int val) {
        if(!root)
            return new TreeNode(val);
        if(val < root->val)
            root->left = insert(root->left, val);
        else
            root->right = insert(root->right, val);
        return root;
    }

    TreeNode* search(TreeNode* root, int val) {
        if(!root || root->val == val)
            return root;
        if(val < root->val)
            return search(root->left, val);
        else
            return search(root->right, val);
    }
};


int main() {
    int input;
    while (true)
    {
        cin >> input;
        if (input == 4)
            break;
        // else if ()
    }
}