#Leet Code# Unique Tree

语言：Python

描述：使用递归实现

 class Solution:
     # @return an integer
     def numTrees(self, n):
         if n == :
             return
         elif n == :
             return
         else:
             part_1 = self.numTrees(n-) *
             part_2 = 

             for i in range(,n-):
                 part_left = self.numTrees(i)
                 part_right = self.numTrees(n -  - i)
                 part_2 += part_left * part_right

             return part_1 + part_2