Java [Leetcode 101]symmetric Tree

Title Description:

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

For example, this binary tree is symmetric:

    1   /   2   2/\/3  4 4  3

But the following are not:

    1   /   2   2   \      3    3

Problem Solving Ideas:

Recursive method

The code is as follows:

/** * 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;        Return  Ismirror (Root.left, root.right);    }    public boolean Ismirror (TreeNode left, TreeNode right) {    if (left = = NULL && right = = null)    return true;
   else if (left = = null)    return false;    else if (right = = null)    return false;    else{    if (left.val! = Right.val)    return false;    Return Ismirror (Left.right, Right.left) && ismirror (Left.left, right.right);}}}    

　　

Java [Leetcode 101]symmetric Tree