DSA/1305. All Elements in Two Binary Search Trees.cpp at main · twopieare/DSA · GitHub

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/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    vector<int> getAllElements(TreeNode* root1, TreeNode* root2) {
        /*stack<TreeNode *> s1, s2;
        vector<int> result;
        while(root1 || root2 || !s1.empty() || !s2.empty()){
            while(root1){
                s1.push(root1);
                root1=root1->left;
            }
            while(root2){
                s2.push(root2);
                root2=root2->left;
            }
            if(s1.empty() || (!s1.empty() && s1.top()->val <= s2.top()->val)){
                root1 = s1.top();
                s1.pop();
                result.push_back(root1->val);
                root1 = root1->right;
            }else{
                root2 = s2.top();
                s2.pop();
                result.push_back(root2->val);
                root2 = root2->right;
            }
        }
        return result;*/

        vector<int> res;
          stack<TreeNode *> s1, s2;

          while (root1 || root2 || !s1.empty() || !s2.empty())
          {
               while (root1 != NULL)
               {
                    s1.push(root1);
                    root1 = root1->left;
               }
               while (root2 != NULL)
               {
                    s2.push(root2);
                    root2 = root2->left;
               }
               if (s2.empty() || (!s1.empty() && s1.top()->val <= s2.top()->val))
               {
                    root1 = s1.top();
                    s1.pop();
                    res.push_back(root1->val);
                    root1 = root1->right;
               }
               else
               {
                    root2 = s2.top();
                    s2.pop();
                    res.push_back(root2->val);
                    root2 = root2->right;
               }
          }
          return res;
    }
};