leetcode-----101. 对称二叉树

• 链接：https://leetcode-cn.com/problems/symmetric-tree/

代码

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool isSymmetric(TreeNode* root) {
        return !root || dfs(root->left, root->right);
    }
    bool dfs(TreeNode* p, TreeNode* q) {
        if (!p || !q) return !p && !q;
        return p->val == q->val && dfs(p->left, q->right) && dfs(p->right, q->left);
    }
};