Leetcode#105 Construct Binary Tree from Preorder and Inorder Traversal

 1 TreeNode *restore(vector<int> &preorder, vector<int> &inorder, int pp, int ip, int len) {
 2   if (len <= 0)
 3     return NULL;
 4 
 5   TreeNode *node = new TreeNode(preorder[pp]);
 6 
 7   if (len == 1)
 8     return node;
 9 
10   int leftLen = 0;
11   while (inorder[ip + leftLen] != preorder[pp])
12     leftLen++;
13   node->left = restore(preorder, inorder, pp + 1, ip, leftLen);
14   node->right = restore(preorder, inorder, pp + leftLen + 1, ip + leftLen + 1, len - leftLen - 1);
15 
16   return node;
17 }
18 
19 TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
20     return restore(preorder, inorder, 0, 0, preorder.size());
21 }