leetcode Symmetric Tree 1.8 难度系数1

最新推荐文章于 2021-01-02 10:53:07 发布

yundomo

最新推荐文章于 2021-01-02 10:53:07 发布

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本文介绍了一种检查二叉树是否为中心对称的方法，通过递归比对左右子树来实现。提供了完整的Java代码示例，并解释了如何解决这一问题。

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Question:

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

For example, this binary tree is symmetric:

But the following is not:

Note:
Bonus points if you could solve it both recursively and iteratively.

confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.

/**
 * Definition for binary tree
 * 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 isSymmetric(root.left,root.right);
    }
    public boolean isSymmetric(TreeNode left,TreeNode right){
    	if(left==null&&right==null){
    		return true;
    	}
    	if(left==null&&right!=null){
    		return false;
    	}
    	if(left!=null&&right==null){
    		return false;
    	}
    	if (left.val!=right.val) {
			return false;
		}else {
			return isSymmetric(left.left,right.right)&&isSymmetric(left.right, right.left);
		}
    	
    }
}