/**

  * Definition for binary tree

  * struct TreeNode {

  *     int val;

  *     TreeNode *left;

  *     TreeNode *right;

  *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}

  * };

  */

 class Solution {

 public:

     TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {

         if(preorder.size()!=inorder.size()) return NULL;

         return build(preorder,inorder,,preorder.size()-,,inorder.size()-);

     }

     TreeNode *build(vector<int> &preorder, vector<int> &inorder,int s1,int e1,int s2,int e2){

         if(s1>e1||s2>e2) return NULL;

         if(s1==e1) return new TreeNode(preorder[s1]);

         TreeNode *res=new TreeNode(preorder[s1]);

         int tmp=preorder[s1];

         int index=;

         while((s2+index)<=e2){

             if(inorder[s2+index]==tmp)

                 break;

             index++;

         }

         res->left=build(preorder,inorder,s1+,s1+index,s2,s2+index-);

         res->right=build(preorder,inorder,s1+index+,e1,s2+index+,e2);

         return res;

     }

 };