LEETCODE: Symmetric Tree

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于 2014-12-29 14:02:16 发布

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文章标签： LEETCODE 算法递归二叉树

本文链接：https://blog.youkuaiyun.com/anyicheng2015/article/details/42237617

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本文介绍了一种算法来判断给定的二叉树是否是对称的，即树的左右子树是否镜像对称。

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

For example, this binary tree is symmetric:

But the following is not:

/**
 * Definition for binary tree
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    bool check(TreeNode *left, TreeNode *right) {
        if(left == NULL && right == NULL)   return true;
        if(left == NULL || right == NULL)   return false;
        
        return left->val == right->val && check(left->left, right->right) && check(left->right, right->left);
    }
    bool isSymmetric(TreeNode *root) {
        if(root == NULL)
            return true;
        return check(root->left, root->right);
    }
};