binary search tree

#include <iostream>
#include <cstdlib>
#include <cmath>
#include <conio.h>

using namespace std;

struct Node {
    string key, value;
    Node *right = NULL, *left = NULL;
    Node(string a, string b) : key(a), value(b) {}
};

Node** treeSearch(Node** tree, string key) {
    if (*tree == NULL || (*tree) -> key == key) return tree;
    if (key > (*tree) -> key) return treeSearch(&((*tree) -> right), key);
    return treeSearch(&((*tree) -> left), key);
}

void treeInsert(Node** tree, string key, string value) {
    if (*tree == NULL) { *tree = new Node(key, value); return; }
    if ((*tree) -> key > key) { treeInsert(&((*tree) -> left), key, value); return; }
    treeInsert(&((*tree) -> right), key, value);
}

Node** treeMin(Node** tree) {
    if ((*tree) -> left == NULL) return tree;
    return treeMin(&((*tree) -> left));
}

void treeDelete(Node** tree) {
    if ((*tree) -> left && (*tree) -> right) {
        Node** p = treeMin(&((*tree) -> right));
        (*tree) -> key = (*p) -> key;
        (*tree) -> value = (*p) -> value;
        treeDelete(p);
        return;
    }
    Node* p;
    if ((*tree) -> left || (*tree) -> right) {
        if ((*tree) -> left) {
            p = (*tree) -> left;
            **tree = *((*tree) -> left);
        } else {
            p = (*tree) -> right;
            **tree = *((*tree) -> right);
        }
        delete p;
        return;
    }
    delete *tree;
    *tree = NULL;
}

void treePrint(Node* tree) {
    if (tree == NULL) return;
    treePrint(tree -> left);
    cout << tree -> key << ": " << tree -> value << endl;
    treePrint(tree -> right);
}

int main() {
    string command, surn, phone;
    Node* tree = NULL;

    while (1) {
        system("CLS");
        cout << "===Telephone directory based on binary search tree===" << endl << endl;

        cout << "add 'surname' 'phone' - add new contact" << endl;
        cout << "remove 'surname' - remove contact" << endl;
        cout << "search 'surname' - search contact" << endl;
        cout << "print - print all contacts" << endl;
        cout << "exit - close program" << endl;

        cout << endl << "<- ";

        cin.clear();
        cin >> command;

        if (command == "exit") break;
        if (command == "print") {
            cout << endl << "All contacts:" << endl;
            treePrint(tree);
            if (tree == NULL) cout << "empty" << endl;
        }
        if (command == "search") {
            cin.clear();
            cin >> surn;
            Node* p = *treeSearch(&tree, surn);
            if (p) cout << endl << p -> key << ": " << p -> value << endl;
            else cout << endl << "there is not" << endl;
        }
        if (command == "remove") {
            cin.clear();
            cin >> surn;
            Node** p = treeSearch(&tree, surn);

            if (*p) {
                treeDelete(p);
                cout << endl << "Removed" << endl;
            } else cout << endl << "there is not" << endl;
        }
        if (command == "add") {
            cin.clear();
            cin >> surn >> phone;
            if (*treeSearch(&tree, surn) == NULL) {
                treeInsert(&tree, surn, phone);
                cout << endl << "Aded" << endl;
            } else cout << endl << "already aded" << endl;
        }
        getch();
    }
    return 0;
}