p101

LeetCode p101 Remove Symmetric Tree 题解

1.题目：

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

For example, this binary tree [1,2,2,3,4,4,3] is symmetric:

1

/ \
2 2
/ \ / \
3 4 4 3

But the following [1,2,2,null,3,null,3] is not:

1

/ \
2 2
\ \
3 3

题意：

判断一个树是否沿中心轴对称。

2.解题思路:

见代码

3.代码

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[title] [] [url] [link text]

 
/**
 * 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 check(root.left, root.right);
	}

	public boolean check(TreeNode left, TreeNode right) {
		if (left == null && right == null)
			return true;
		if (left == null || right == null)
			return false;
		if (left.val != right.val)
			return false;
		return check(left.left, right.right) && check(left.right, right.left);
	}
}

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4.一些总结：