LeetCode：105_Construct Binary Tree from Preorder and Inorder Traversal | 根据前序和中序遍历构建二叉树 | Medium

要求：通过二叉树的前序和中序遍历序列构建一颗二叉树

代码如下：

 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;
 }