# Leetcode 1305. All Elements in Two Binary Search Trees
###### tags: `Leetcode(JAVA)`

題目 : https://leetcode.com/problems/all-elements-in-two-binary-search-trees/ 。

想法 :

先走訪再排序。

時間複雜度 : O(nlogn)。

程式碼 : (JAVA)

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode() {}
 *     TreeNode(int val) { this.val = val; }
 *     TreeNode(int val, TreeNode left, TreeNode right) {
 *         this.val = val;
 *         this.left = left;
 *         this.right = right;
 *     }
 * }
 */
class Solution {
    List<Integer> ans = new ArrayList<Integer>();
    
    void travel(TreeNode root){
        if(root == null) return;
        else{
            ans.add(root.val);
            travel(root.left);
            travel(root.right);
        }
    }
    
    public List<Integer> getAllElements(TreeNode root1, TreeNode root2) {
        travel(root1);
        travel(root2);
        
        int l = ans.size();
        Collections.sort(ans);
        
        return ans;  
    }
}