/**
* 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:intmaxDepth(TreeNode* root){return root ?max(maxDepth(root->left),maxDepth(root->right))+1:0;}};
/**
* 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:
unordered_map<int,int> pos;
TreeNode*buildTree(vector<int>& preorder, vector<int>& inorder){int n = preorder.size();for(int i =0; i < n; i ++)
pos[inorder[i]]= i;returndfs(preorder, inorder,0, n -1,0, n -1);}
TreeNode*dfs(vector<int>&pre, vector<int>&in,int pl,int pr,int il,int ir){if(pl > pr)returnNULL;int k = pos[pre[pl]]- il;
TreeNode* root = new TreeNode(pre[pl]);//前序的第一个节点为根节点
root->left =dfs(pre, in, pl +1, pl + k, il, il + k -1);
root->right =dfs(pre, in, pl + k +1, pr, il + k +1, ir);return root;}};
/**
* 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:
unordered_map<int,int> pos;
TreeNode*buildTree(vector<int>& inorder, vector<int>& postorder){int n = inorder.size();for(int i =0; i < n; i ++)
pos[inorder[i]]= i;returndfs(postorder, inorder,0, n -1,0, n -1);}
TreeNode*dfs(vector<int>&post, vector<int>&in,int pl,int pr,int il,int ir){if(pl > pr)returnNULL;int k = pos[post[pr]]- il;
TreeNode* root = new TreeNode(post[pr]);
root->left =dfs(post, in, pl, pl + k -1, il, il + k -1);
root->right =dfs(post, in, pl + k, pr -1, il + k +1, ir);return root;}};