[LeetCode] Same Tree、Symmetric Tree

最新推荐文章于 2025-06-17 16:34:26 发布

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最新推荐文章于 2025-06-17 16:34:26 发布

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本文介绍了一种检查二叉树是否相同及是否为镜像对称的方法。对于相同二叉树的判断，主要通过递归比较两棵树的节点值及左右子树是否完全一致；对于对称二叉树的判断，则需验证树的左子树是否为右子树的镜像。

Same Tree:

Given two binary trees, write a function to check if they are equal or not.

Two binary trees are considered equal if they are structurally identical and the nodes have the same value.

/**
 * 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 isSameTree(TreeNode *p, TreeNode *q) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
    	if (!p || !q)
			return !p&&!q;
		return (p->val==q->val)
			&& isSameTree(p->left,q->left)
			&& isSameTree(p->right,q->right);
    }
};

Symmetric Tree：

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:

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

/**
 * 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 isSymmetric(TreeNode *root) {
        // Start typing your C/C++ solution below
        // DO NOT write int main() function
        
    	if ( !root )
			return true;
		return isSym(root->left,root->right);
    }
	bool isSym(TreeNode* p,TreeNode* q)
	{
		if (!p||!q)
			return !p&&!q;
		return p->val==q->val
			&& isSym(p->left,q->right)
			&& isSym(p->right,q->left);
	}
};