1. /**
    2.  * Definition for a binary tree node.
    3.  * function TreeNode(val, left, right) {
    4.  *     this.val = (val===undefined ? 0 : val)
    5.  *     this.left = (left===undefined ? null : left)
    6.  *     this.right = (right===undefined ? null : right)
    7.  * }
    8.  */
    9. /**
    10.  * @param {TreeNode} root1
    11.  * @param {TreeNode} root2
    12.  * @return {number[]}
    13.  */
    14. var getAllElements = function(root1, root2) {
    15.     let arr_left = []
    16.     let arr_right = []
    17.     let dfs = (data, arr) => {
    18.         if (data) {
    19.             dfs(data.left, arr)
    20.             dfs(data.right, arr)
    21.             arr.push(data.val)
    22.         }
    23.     }
    24.     dfs(root1, arr_left)
    25.     dfs(root2, arr_right)
    26.     return arr_left.concat(arr_right).sort((a, b) => {return a - b})
    27. };

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