Unique Binary Search Trees II.md

Given an integer n, generate all structurally unique BST's (binary search trees) that store values 1 ... n.

Example:

Input: 3 Output: [ [1,null,3,2], [3,2,null,1], [3,1,null,null,2], [2,1,3], [1,null,2,null,3] ] Explanation: The above output corresponds to the 5 unique BST's shown below:

1 3 3 2 1 \ / / / \
3 2 1 1 3 2 / / \
2 1 2 3

My code:

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

class Solution:
    def generateTrees(self, n):
        """
        :type n: int
        :rtype: List[TreeNode]
        """
        if n==0:
            return []
        self.final=self.Set_node(1,n)
        return self.final
    def Set_node(self,start,end):
        if start>end:
            return [None,]
        all_trees=[]
        for i in range(start,end+1):
            left_trees=self.Set_node(start,i-1)
            right_trees=self.Set_node(i+1,end)
            for l in left_trees:
                for r in right_trees:
                    current=TreeNode(i)
                    current.left=l
                    current.right=r
                    all_trees.append(current)
        return all_trees
        
        

Solution: https://leetcode.com/problems/unique-binary-search-trees-ii/