題目描述

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.

合並兩棵二叉樹，如果兩棵樹都在同一位置有結點，則把結點相加，如果沒有，則把有的結點來代替，其實就是一個遞歸的算法

代碼如下

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