【二叉树】【递归】101.对称二叉树

Java二叉树对称性判断算法

原创已于 2025-08-17 15:48:09 修改 · 252 阅读

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#二叉树的

于 2023-12-06 22:16:06 首次发布

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本文介绍了一个Java程序，通过`isSymmetric`方法和`myJudge`辅助函数，使用递归实现判断给定二叉树是否对称的算法。核心逻辑是通过比较左右子节点的值和结构来确定对称性。

题目

Python

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def isSymmetric(self, root: Optional[TreeNode]) -> bool:
        if not root:
            return True
        return self.judge(root.left, root.right)

    def judge(self, left, right):
        if not left and not right:
            return True
        elif not left or not right:
            return False
        elif left.val != right.val:
            return False
        return self.judge(left.left, right.right) and self.judge(left.right, right.left)

Java

法1:基本好法

class Solution {
    public boolean isSymmetric(TreeNode root) {
        if (root == null || (root.left == null && root.right == null)) {
            return true;
        }
        return myJudge(root.left, root.right);
    }

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