Merge Two Binary Trees——LeetCode进阶路

原题链接https://leetcode.com/problems/merge-two-binary-trees/

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.

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.

思路分析

从两个树的根节点开始，对应节点相加……很朴素的一题了

源码附录

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;v1.
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
class Solution {
    public TreeNode mergeTrees(TreeNode t1, TreeNode t2) {
        if(t1==null && t2==null)
        {
            return null;
        }
        if(t1==null || t2==null)
        {
            return t1==null ? t2 :t1;    
        }
        
        t1.val = t1.val + t2.val;
        t1.left = mergeTrees(t1.left,t2.left);
        t1.right = mergeTrees(t1.right,t2.right);
        return t1;
    }
}