不同的二叉搜索树 II

Python

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def generateTrees(self, n):
        """
        :type n: int
        :rtype: List[TreeNode]
        """
        if n <= 0 :return []
        nums = range(1,n+1)
        return self.generateSubTree(nums)
    def generateSubTree(self,num_list):
        ans = []
        if not num_list:return [None]
        for index in range(len(num_list)):
            left_list = self.generateSubTree(num_list[:index])
            right_list = self.generateSubTree(num_list[index+1:])
            for i in left_list:
                for j in right_list:
                    tree = TreeNode(num_list[index])
                    tree.left = i
                    tree.right = j
                    ans.append(tree)      
        return ans