Palindrome Construct Binary Tree from Preorder and Inorder Traversal

// 156ms 过大的
 1 /**
 2  * Definition for binary tree
 3  * struct TreeNode {
 4  *     int val;
 5  *     TreeNode *left;
 6  *     TreeNode *right;
 7  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 8  * };
 9  */
10 class Solution {
11 public:
12 
13     TreeNode *buildTree(vector<int> &preorder,int pb,int pe, vector<int> &inorder,int ib,int ie)
14     {
15         TreeNode *root=new TreeNode(0);
16         root->val=preorder[pb];
17         
18         vector<int>::iterator proot=find(inorder.begin(),inorder.end(),root->val);
19         int pos=proot-inorder.begin();
20         
21         int leftLen=pos-ib;
22         int rightLen=ie-pos;
23         
24         if(leftLen>0)
25             root->left=buildTree(preorder,pb+1,pb+leftLen,inorder,ib,pos-1);
26         if(rightLen>0)
27             root->right=buildTree(preorder,pb+leftLen+1,pe,inorder,pos+1,ie);
28         return root;
29     }
30     
31     TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
32         // Start typing your C/C++ solution below
33         // DO NOT write int main() function
34         if(preorder.size()==0)
35             return NULL;
36         return buildTree(preorder,0,preorder.size()-1,inorder,0,preorder.size()-1);
37     }
38 };