Leetcode_1305_All Elements in Two Binary Search Trees

[lihe]

All Elements in Two Binary Search Trees

Given two binary search trees root1 and root2.

Return a list containing all the integers from both trees sorted in ascending order.

Example 1:

Input: root1 = [2,1,4], root2 = [1,0,3]
Output: [0,1,1,2,3,4]

Example 2:

Input: root1 = [0,-10,10], root2 = [5,1,7,0,2]
Output: [-10,0,0,1,2,5,7,10]

Example 3:

Input: root1 = [], root2 = [5,1,7,0,2]
Output: [0,1,2,5,7]

Example 4:

Input: root1 = [0,-10,10], root2 = []
Output: [-10,0,10]

Example 5:

Input: root1 = [1,null,8], root2 = [8,1]
Output: [1,1,8,8]

Constraints:

• Each tree has at most 5000 nodes.
• Each node's value is between [-10^5, 10^5].

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {

    List<Integer> result = new ArrayList<>();

    public List<Integer> getAllElements(TreeNode root1, TreeNode root2) {

        if(root1 == null && root2 == null)
            return result;

        helper(root1);
        helper(root2);
        Collections.sort(result);

        return result;
    }


    private void helper(TreeNode root){
        if(root == null)
            return;
        else {
            result.add(root.val);
            helper(root.left);
            helper(root.right);
        }
    }
}