struct TreeNode {

     int            val;

     TreeNode    *left;

     TreeNode    *right;

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

 };

 typedef vector<int>::iterator Iter;

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

 {

     return buildTreeRecur(preorder.begin(), preorder.end(), inorder.begin(), inorder.end());

 }

 TreeNode *buildTreeRecur(Iter pstart, Iter pend, Iter istart, Iter iend)

 {

     if(pstart == pend || istart == iend)

         return NULL;

     int ival = *pstart;

     Iter ipos = find(istart, iend, ival);

     TreeNode *res = new TreeNode(ival);

     res->left = buildTreeRecur(pstart + , pstart++(ipos-istart), istart, ipos);

     res->right = buildTreeRecur(pstart++(ipos-istart), pend, ipos+, iend);

     return res;

 }