方法1:递归
时间复杂度:$O(n)$
空间复杂度:$O(n)$
解题思路
https://leetcode.cn/problems/symmetric-tree/solution/dui-cheng-er-cha-shu-by-leetcode-solution/
Java 代码
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode() {}
* TreeNode(int val) { this.val = val; }
* TreeNode(int val, TreeNode left, TreeNode right) {
* this.val = val;
* this.left = left;
* this.right = right;
* }
* }
*/
class Solution {
public boolean isSymmetric(TreeNode root) {
return check(root, root);
}
public boolean check(TreeNode p, TreeNode q) {
if (p == null & q == null) {
return true;
} else if (p == null || q == null) {
return false;
} else if (p.val != q.val) {
return false;
} else {
return check(p.left, q.right) && check(p.right, q.left);
}
}
}