617. Merge Two Binary Trees

最新推荐文章于 2020-05-10 14:18:51 发布

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最新推荐文章于 2020-05-10 14:18:51 发布

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分类专栏： leetcode 文章标签： tree

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本文介绍了一种合并两棵二叉树的方法，当两棵树有相同位置的节点时，将这两个节点的值相加作为新节点的值；若只有一个树有节点，则直接采用该节点作为新节点。使用递归方式实现这一过程。

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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.

Example 1:

Input: 
	Tree 1                     Tree 2                  
          1                         2                             
         / \                       / \                            
        3   2                     1   3                        
       /                           \   \                      
      5                             4   7                  
Output: 
Merged tree:
	     3
	    / \
	   4   5
	  / \   \ 
	 5   4   7

Note:The merging process must start from the root nodes of both trees.

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合并两棵二叉树，重合部分相加。这里使用递归的方法。为了不构造新的节点，使用给出的两棵树的节点。

代码：

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

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