基本二叉树操作。
O[ ][ ]
[ ]O[ ]
代码：
TreeNode *restore(vector<int> &preorder, vector<int> &inorder, int pp, int ip, int len) {
if (len <= )
return NULL;
TreeNode *node = new TreeNode(preorder[pp]);
if (len == )
return node;
int leftLen = ;
while (inorder[ip + leftLen] != preorder[pp])
leftLen++;
node->left = restore(preorder, inorder, pp + , ip, leftLen);
node->right = restore(preorder, inorder, pp + leftLen + , ip + leftLen + , len - leftLen - );
return node;
}
TreeNode *buildTree(vector<int> &preorder, vector<int> &inorder) {
return restore(preorder, inorder, , , preorder.size());
}