leetcode-cpp 101. Symmetric Binary Tree

101. Symmetric Binary Tree

• topic:

• link

  leetcode

• solution:

  At first glance, this question is quite simple, but the result is a bit confusing because the writing is not clear.

  Finally, think about the symmetry of a tree? Wouldn't it be split into two trees? How can two trees be compared symmetrically? You can use a queue!

  One throws the left child in, and the other throws the right child in, taking the head every time. Isn't it more symmetrical? Need to pay attention to these points:

  • Throw roots twice the first time
  • When throwing left child, right child, there is no need to judge whether it is NULL or not. It is unified to judge these things by judging before throwing.
    • Both are NULL, no problem!
    • Only one is NULL, I'm sorry, please rest.
    • Is the value different? Bye bye!

• code

class Solution {
public:
	bool isSymmetric(TreeNode* root) {
		queue<TreeNode*> q;
		q.push(root);
		q.push(root);
		while (!q.empty())
		{
			auto t1 = q.front();
			q.pop();
			auto t2 = q.front();
			q.pop();
			if (!t1 && !t2) continue;
			if (!t1 || !t2)
				return false;
			if (t1->val != t2->val)
				return false;//帅啊
			q.push(t1->left);
			q.push(t2->right);
			q.push(t1->right);
			q.push(t2->left);
		}
		return true;
	}
};