[LeetCode]题解（python）：095-Unique Binary Search Trees II

# 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 []
        def solve(begin,end):
            if begin > end:
                return [None]
            i = begin
            ans = []
            while i <= end:
                tmp1,tmp2 = solve(begin, i - 1),solve(i + 1,end)
                for j in tmp1:
                    for k in tmp2:
                        tmp = TreeNode(i)
                        tmp.left = j
                        tmp.right = k
                        ans.append(tmp)
                i += 1
            return ans
        return solve(1,n)