leetcode95

class Solution:
    def generateTree(self,s,e) -> 'List[TreeNode]':
        re = []
        if s > e:
            re.append(None)
            return re
        for i in range(s,e+1):
            left = self.generateTree(s,i-1)
            right = self.generateTree(i+1,e)
            for l in left:
                for r in right:
                    root = TreeNode(i)
                    root.left = l
                    root.right = r
                    re.append(root)
        return re

    def generateTrees(self, n: int) -> 'List[TreeNode]':
        if n < 1:
            return list()
        return self.generateTree(1,n)

分治法