目录
101. 对称二叉树
92% 100%
/**
* 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 ans;
void dfs(TreeNode *Left,TreeNode *Right){
if(!ans) return ;
if(Left==NULL && Right==NULL){
ans=true; return ;
}
if(Left==NULL || Right==NULL) {ans=false; return ;}
if(Left->val!=Right->val){
ans=false; return ;
}
dfs(Left->left,Right->right);
dfs(Left->right,Right->left);
}
bool isSymmetric(TreeNode* root) {
if(root==NULL) return true;
ans=true;
dfs(root->left,root->right);
return ans;
}
};100. 相同的树
跟上个题一样，就改了2行代码
100% 100%
/**
* 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 {
private:
bool ans;
void dfs(TreeNode *Left,TreeNode *Right){
if(!ans) return ;
if(Left==NULL && Right==NULL){
ans=true; return ;
}
if(Left==NULL || Right==NULL) {ans=false; return ;}
if(Left->val!=Right->val){
ans=false; return ;
}
dfs(Left->left,Right->left);
dfs(Left->right,Right->right);
}
public:
bool isSameTree(TreeNode* p, TreeNode* q) {
ans=true;
dfs(p,q);
return ans;
}
};104. 二叉树的最大深度
72% 100%
class Solution {
private:
int cnt,tmp;
void dfs(TreeNode *cur){
if(cur->left==NULL && cur->right==NULL){
if(cnt<tmp) cnt=tmp; //cur = leaf
return ;
}
if(cur->left){
tmp++;
dfs(cur->left);
tmp--;
}
if(cur->right){
tmp++;
dfs(cur->right);
tmp--;
}
}
public:
int maxDepth(TreeNode* root) {
if(root==NULL) return 0;
cnt=0;tmp=1;
dfs(root);
return cnt;
}
};102. 二叉树的层序遍历
89.22% 100.00%
ans.push_back(vector<int>()); ？
class Solution {
public:
vector<vector<int>> levelOrder(TreeNode* root) {
if(root==NULL) return {};
queue<TreeNode *> qu;
qu.push(root);
int level=0;
vector<vector<int>> ans;
while(!qu.empty()){
int len=qu.size();
ans.push_back(vector<int>());
for(int i=0;i<len;i++){
TreeNode *cur=qu.front();qu.pop();
ans[level].push_back(cur->val);
if(cur->left!=NULL){
qu.push(cur->left);
}
if(cur->right!=NULL){
qu.push(cur->right);
}
}
level++;
}
return ans;
}
};