Predecessor And Successor

#include <bits/stdc++.h> 
/*************************************************************

    Following is the Binary Tree node structure

    template <typename T>

    class BinaryTreeNode
    {
    public :
        T data;
        BinaryTreeNode<T> *left;
        BinaryTreeNode<T> *right;

        BinaryTreeNode(T data) {
            this -> data = data;
            left = NULL;
            right = NULL;
        }

        ~BinaryTreeNode() {
            if (left)
            {
                delete left;
            }
            if (right)
            {
                delete right;
            }
        }
    };

*************************************************************/

void solve(BinaryTreeNode<int>*root,int key,int &pre,int &suc)
{
       if(root==nullptr)
        {
            return;
        }
       solve(root->left,key,pre,suc);
        if(root->data<key)
        {
            pre=root->data;
        }
        if(root->data>key and suc==-1)
        {
            suc=root->data;
        }
       solve(root->right,key,pre,suc);
      
}
pair<int,int> predecessorSuccessor(BinaryTreeNode<int>* root, int key)
{
    // Write your code here.
    int pre=-1;
int suc=-1;
    if(root==nullptr)
    {
      return {-1, -1};
    }
    solve(root,key,pre,suc);
    return {pre, suc};
}