题目描述

Given two binary trees and imagine that when you put one of them to cover the other, some nodes of the two trees are overlapped while the others are not.

You need to merge them into a new binary tree. The merge rule is that if two nodes overlap, then sum node values up as the new value of the merged node. Otherwise, the NOT null node will be used as the node of new tree.

合并两棵二叉树，如果两棵树都在同一位置有结点，则把结点相加，如果没有，则把有的结点来代替，其实就是一个递归的算法

代码如下

class Solution {
public:
　　TreeNode* mergeTrees(TreeNode* t1, TreeNode* t2) {
　　　　if (!t1) return t2;
　　　　if (!t2) return t1;

　　　　TreeNode* node = new TreeNode(t1->val + t2->val);
　　　　node->left = mergeTrees(t1->left, t2->left);
　　　　node->right = mergeTrees(t1->right, t2->right);
　　　　return node;
　　}
};

19.Merge Two Binary Trees