leetcode1008

class Solution:
    def __init__(self):
        self.root = None

    def construct(self,order,root,i):
        if i==len(order):
            return None
        else:
            if self.root==None:
                self.root = TreeNode(order[i])
                self.construct(order,self.root,i+1)
            else:
                if order[i]<root.val:
                    if root.left==None:
                        root.left = TreeNode(order[i])
                        self.construct(order,self.root,i+1)
                    else:
                        self.construct(order,root.left,i)
                else:
                    if root.right==None:
                        root.right = TreeNode(order[i])
                        self.construct(order,self.root,i+1)
                    else:
                        self.construct(order,root.right,i)

    def bstFromPreorder(self, preorder: 'List[int]') -> 'TreeNode':
        self.construct(preorder,self.root,0)
        return self.root

比较简单的题目，递归方式构造二叉搜索树。