226. 翻转二叉树 - 力扣（LeetCode）

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if(!root)return root;
        queue<TreeNode*> q;
        q.push(root);
        while(!q.empty()){
            TreeNode* node=q.front();
            q.pop();
            swap(node->left,node->right);
            if(node->left)q.push(node->left);
            if(node->right)q.push(node->right);
        }
        return root;
    }
};

101. 对称二叉树 - 力扣（LeetCode）

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    bool isSymmetric(TreeNode* root) {
        if(!root)return true;
        queue<TreeNode*> q;
        q.push(root->left);
        q.push(root->right);
        while(!q.empty()){
            TreeNode* node1=q.front();q.pop();
            TreeNode* node2=q.front();q.pop();
            if(!node1&&!node2)continue;
            if(!node1||!node2)return false;
            if(node1->val!=node2->val)return false;
            q.push(node1->left);
            q.push(node2->right);
            q.push(node1->right);
            q.push(node2->left);
        }
        return true;
    }
};

剩下的两题我已经在上一天的笔记中写过。