Leetcode Symmetric Tree

最新推荐文章于 2020-12-28 22:34:43 发布

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本文介绍了一种检查二叉树是否为中心对称的方法，通过递归算法判断树的左子树和右子树是否互为镜像。示例展示了如何通过递归方式实现这一功能，并给出了具体的代码实现。

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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 [1,2,2,3,4,4,3] is symmetric:

But the following [1,2,2,null,3,null,3] is not:

Note:
Bonus points if you could solve it both recursively and iteratively.

递归大法，代码如下：

/**
 * 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 symetric(root->left,root->right);
    }
    
    bool symetric(TreeNode* left,TreeNode* right)
    {
        if(left == NULL || right == NULL)
            return left == right;
        else if(left->val == right->val)
        {
            return symetric(left->left,right->right) && symetric(left->right,right->left);
        }
        else
            return false;
    }
};