Leetcode::Construct Binary Tree from Preorder and Inorder Traversal

/**
* 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 *build( vector<int>&preorder,vector<int> &inorder,int start,int end,int start1,int end1)
{
if(start==end)
return NULL;

int i;
TreeNode * tmp = new TreeNode(preorder[start]);

for(i=start1; i<end1; i++)
{
if( inorder[i]==preorder[start])
break;
}

int len = i - start1;

TreeNode *left=build(preorder,inorder,start+1,start+1+len,start1,i);
TreeNode *right=build(preorder,inorder,start+1+len,end,i+1,end1);
tmp->left=left;
tmp->right=right;
return tmp;

}
TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
// Start typing your C/C++ solution below
// DO NOT write int main() function
return build(preorder,inorder,0,preorder.size(),0,inorder.size());
}
};