题目:

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree is symmetric:

    1
   / \
  2   2
 / \ / \
3  4 4  3
But the following is not:
    1
   / \
  2   2
   \   \
   3    3

思路:

  • 首先这是一个求关于中心成对称二叉树的题目
  • 二叉树的思路就是找到一个递归的突破口
  • 首先判断left和right节点的关系来判断,以及(left.left,right.right)以及(left.right,right.left)的关系

代码:

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Solution {
    public boolean isSymmetric(TreeNode root) {
        if(root == null){
            return true;
        }else{
            return isEqual(root.left,root.right);
        }
    }
    public boolean isEqual(TreeNode left,TreeNode right){
        if(left == null){
            return right == null;
        }
        if(right == null){
            return left == null;
        }
        if(left.val != right.val){
            return false;
        }
        if(!isEqual(left.left,right.right)){
            return false;
        }
        if(!isEqual(left.right,right.left)){
            return false;
        }
        return true;
    }
}

LeetCode(25)-symmetric tree的更多相关文章

  1. LeetCode(1) Symmetric Tree

    从简单的道题目開始刷题目: Symmetric Tree 题目:Given a binary tree, check whether it is a mirror of itself (ie, sym ...

  2. LeetCode(101)Symmetric Tree

    题目 Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center). Fo ...

  3. LeetCode(107) Binary Tree Level Order Traversal II

    题目 Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from l ...

  4. LeetCode(103) Binary Tree Zigzag Level Order Traversal

    题目 Given a binary tree, return the zigzag level order traversal of its nodes' values. (ie, from left ...

  5. LeetCode(124) Binary Tree Maximum Path Sum

    题目 Given a binary tree, find the maximum path sum. For this problem, a path is defined as any sequen ...

  6. LeetCode(26)-Binary Tree Level Order Traversal II

    题目: Given a binary tree, return the bottom-up level order traversal of its nodes' values. (ie, from ...

  7. LeetCode(102) Binary Tree Level Order Traversal

    题目 Given a binary tree, return the level order traversal of its nodes' values. (ie, from left to rig ...

  8. LeetCode(100) Same Tree

    题目 Given two binary trees, write a function to check if they are equal or not. Two binary trees are ...

  9. LeetCode(25)Reverse Nodes in k-Group

    题目 Given a linked list, reverse the nodes of a linked list k at a time and return its modified list. ...

随机推荐

  1. Android必知必会-带列表的地图POI周边搜索

    如果移动端访问不佳,请尝试–> Github版 2016-08-22 更新 注意:在 Activity 代码中的onPoiSearched(PoiResult result, int rCode ...

  2. memcached实战系列(七)理解Memcached的数据过期方式、新建过程、查找过程

    1.1.1. 新建Item分配内存过程 1:快速定位slab classid,先计算Item长度 key键长+flag+suffix(16字节)+value值长+结构大小(32字节),如90byte ...

  3. UE4读取本地XML文件

    其实这里读取XML也是利用了Tinyxml来读取xml,主要是讲Tinyxml放在UE4中,遇到的一点点坑 1.先给出Tinyxml链接:http://www.grinninglizard.com/t ...

  4. Servlet之cookie处理

    Cookies 通常设置在 HTTP 头信息中(虽然JavaScript 也可以直接在浏览器上设置一个 Cookie).设置 Cookie 的 Servlet 会发送如下的头信息: HTTP/1.1 ...

  5. iPhone全部设备分辨率速查

    大熊猫猪·侯佩原创或翻译作品.欢迎转载,转载请注明出处. 如果觉得写的不好请多提意见,如果觉得不错请多多支持点赞.谢谢! hopy ;) 免责申明:本博客提供的所有翻译文章原稿均来自互联网,仅供学习交 ...

  6. 谈谈spring的缓存

    缓存到底扮演了什么角色 请移步:  http://hacpai.com/article/1376986299174 在对项目进行优化的时候,我们可以主要从以下三个方面入手: 1 缓存 2 集群 3 异 ...

  7. Java数据类型及类型转换

    http://blog.csdn.net/pipisorry/article/details/51290064 java浮点数保留n位小数 import java.text.DecimalFormat ...

  8. 03 ProgressBar 进度条

    >      style="?android:attr/progressBarStyleSmall" 样式                 android:progress= ...

  9. Java创建柱状图及饼状图

    Java创建图表其实还是很方便的,但是要引入相关的jar包.如下 jfreechart.jar jcommon,jar gnujaxp.jar 其中最主要的是jfreechart.jar. 下面就让我 ...

  10. Java中常用的正则表达式

    常用的正则表达式 匹配中文字符的正则表达式: [\u4e00-\u9fa5] 匹配双字节字符(包括汉字在内):[^\x00-\xff] 匹配空行的正则表达式:\n[\s| ]*\r 匹配HTML标记的 ...