题目描述

和leetcode226.翻转二叉树非常相似，核心还是递归。
答案：

    class Solution {public TreeNode mergeTrees(TreeNode root1, TreeNode root2) {if (root1 == null) {return root2;}if (root2 == null) {return root1;}TreeNode root = new TreeNode();root.val = root1.val + root2.val;root.left = mergeTrees(root1.left, root2.left);root.right = mergeTrees(root1.right, root2.right);return root;}}