LeetCode 101 Symmetric Tree

LeetCode 101

Symmetric Tree

• Problem Description：
  判断给出的二叉树是否是对称二叉树。

  具体的题目信息：
  https://leetcode.com/problems/symmetric-tree/description/

• Example:
  
• Solution:

/**
 * 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) {
        if (root == NULL) return true;
        return Symmetric(root->left, root->right);
    }
    bool Symmetric(TreeNode* l, TreeNode* r) {
        if (l == NULL && r == NULL) return true;
        if (l == NULL || r == NULL) return false;
        if (l->val == r->val) return Symmetric(l->left, r->right) &&Symmetric(l->right, r->left);
        return false;
    }
};