<p>Given two binary search trees <code>root1</code> and <code>root2</code>, return <em>a list containing all the integers from both trees sorted in <strong>ascending</strong> order</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2019/12/18/q2-e1.png" style="width: 457px; height: 207px;" />
<pre>
<strong>Input:</strong> root1 = [2,1,4], root2 = [1,0,3]
<strong>Output:</strong> [0,1,1,2,3,4]
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2019/12/18/q2-e5-.png" style="width: 352px; height: 197px;" />
<pre>
<strong>Input:</strong> root1 = [1,null,8], root2 = [8,1]
<strong>Output:</strong> [1,1,8,8]
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li>The number of nodes in each tree is in the range <code>[0, 5000]</code>.</li>
	<li><code>-10<sup>5</sup> &lt;= Node.val &lt;= 10<sup>5</sup></code></li>
</ul>

/**
 * 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) {

        //
        vector<int>ans;
        stack<TreeNode*>st1;
        stack<TreeNode*>st2;

        while(root1){
            st1.push(root1);
            root1=root1->left;
        }

        while(root2){
            st2.push(root2);
            root2=root2->left;
        }

        while(!st1.empty() && !st2.empty()){

            //s1==s2

            if(st1.top()->val==st2.top()->val){

             ans.push_back(st1.top()->val);
             ans.push_back(st1.top()->val);

             root1=st1.top()->right;
             root2=st2.top()->right;

             st1.pop(), st2.pop();

            }
            //s1>s2
            else if(st1.top()->val<st2.top()->val){
                ans.push_back(st1.top()->val);
                root1=st1.top()->right;
                st1.pop();
            }
            //s1>s2
            else{
               ans.push_back(st2.top()->val);
                root2=st2.top()->right;
                st2.pop();
            }

            while(root1){
            st1.push(root1);
            root1=root1->left;
            }

            while(root2){
            st2.push(root2);
            root2=root2->left;
            }
        }

        //check for which stack is remaining 
        while(!st1.empty()){
            ans.push_back(st1.top()->val);
            root1=st1.top()->right;
            st1.pop();

            
            while(root1){
            st1.push(root1);
            root1=root1->left;
            }
        }

         while(!st2.empty()){
            ans.push_back(st2.top()->val);
            root2=st2.top()->right;
            st2.pop();

            while(root2){
            st2.push(root2);
            root2=root2->left;
            }
        }

        return ans;
    }
};
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