102. 二分木のレベル順走査
/**
* 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:
vector<vector<int>> levelOrder(TreeNode* root) {
queue<TreeNode*>que;
vector<vector<int>>res;
if(root!=nullptr){
que.push(root);
}
while(!que.empty()){
int size=que.size();
vector<int>vec;
for(int i=0;i<size;i++){
TreeNode* node=que.front();
que.pop();
if(node->left!=nullptr)que.push(node->left);
if(node->right!=nullptr)que.push(node->right);
vec.push_back(node->val);
}
res.push_back(vec);
}
return res;
}
};
逆二分木
/**
* 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==nullptr)return root;
swap(root->left,root->right);
invertTree(root->left);
invertTree(root->right);
return root;
}
};
対称二分木
/**
* 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 {
bool backing(TreeNode*left,TreeNode*right){
if(left==nullptr&&right!=nullptr)return false;
else if(left!=nullptr&&right==nullptr)return false;
else if(left==nullptr&&right==nullptr)return true;
else if(left->val!=right->val)return false;
bool leftbool=backing(left->left,right->right);
bool rightbool=backing(left->right,right->left);
return leftbool&&rightbool;
}
public:
bool isSymmetric(TreeNode* root) {
return backing(root->left,root->right);
}
};