text: '''
  Note: This is an extension of House Robber.
  
  After robbing those houses on that street, the thief has found himself a new place for his thievery so that he will not get too much attention. This time, all houses at this place are arranged in a circle. That means the first house is the neighbor of the last one. Meanwhile, the security system for these houses remain the same as for those in the previous street.
  
  Given a list of non-negative integers representing the amount of money of each house, determine the maximum amount of money you can rob tonight without alerting the police.
  
  '''
  
  class Solution:
      # @param {integer[]} nums
      # @return {integer}
      def rob_helper(self, nums, start, end):
          pre = 0; cur = 0
          for i in xrange(start, end):
              tmp = pre
              pre = cur
              cur = max(tmp+nums[i], pre)
          return max(pre, cur)
          
      def rob(self, nums):
          n = len(nums)
          if n == 0 : return 0
          if n == 1 : return nums[0]
          return max(self.rob_helper(nums, 0, n-1), self.rob_helper(nums, 1, n))
  
  
  # test case: [1] or [0]
  # test case: [2,1,1,2]
  
  # Reference: https://leetcode.com/discuss/36544/simple-ac-solution-in-java-in-o-n-with-explanation
  