https://www.geeksforgeeks.org/batch/gfg-160-problems/track/tree-gfg-160/problem/find-a-pair-with-given-target-in-bst

class Solution {
  public:
    bool findTarget(Node *root, int target) {
        // your code here.
        vector<int > res ;
        
        helper(root , res);
        
        int left =0 ;
        int right= res.size() -1;
        
        while(left < right ){
            if(res[left] + res[right] == target){
                return true;
            }else if(res[left] + res[right] < target){
                left++;
            }else right--;
            
        }
        
        return false;
    }
    
    private: 
        void helper(Node* root , vector<int> & res){
            if(!root) return;
            
            helper(root->left , res);
            res.push_back(root->data );
            helper(root->right , res);
        }
    
    
};

Time & Space Complexity:

• Time: O(n) – In-order traversal and two-pointer scan.
• Space: O(n) – Extra space for the nums array.