# [617. Merge Two Binary Trees](https://leetcode.com/problems/merge-two-binary-trees/) # 思路 合并两个二叉树。就是一个很简单的递归: * 若`t1`和`t2`任意一个为空,那么直接返回另一个即可(递归出口); * 否则,将`t1`的值加上`t2`的值,然后递归合并`t1`和`t2`的左子树以及`t1`和`t2`的右子树。 # C++ ``` C++ class Solution { public: TreeNode* mergeTrees(TreeNode* t1, TreeNode* t2) { if(t1 == NULL) return t2; if(t2 == NULL) return t1; t1 -> val += t2 -> val; t1 -> left = mergeTrees(t1 -> left, t2 -> left); t1 -> right = mergeTrees(t1 -> right, t2 -> right); delete t2; return t1; } }; ```