House Robber II

You are a professional robber planning to rob houses along a street. Each house has a certain amount of money stashed. All houses at this place arearranged in a circle.That means the first house is the neighbor of the last one. Meanwhile, adjacent houses have security system connected and it will automatically contact the police if two adjacent houses were broken into on the same night.

Given a list of non-negative integers representing the amount of money of each house, determine the maximum amount of money you can rob tonightwithout alerting the police.

Example 1:

Input:
 [2,3,2]

Output:
 3

Explanation:
 You cannot rob house 1 (money = 2) and then rob house 3 (money = 2),
             because they are adjacent houses.

Example 2:

Input:
 [1,2,3,1]

Output:
 4

Explanation:
 Rob house 1 (money = 1) and then rob house 3 (money = 3).
             Total amount you can rob = 1 + 3 = 4.

分析

拆环：1.去头一个数组，去尾一个数组 2.double数组，然后一个window，长度是数组长度

注意这里yes 和No交换进行的方法

class Solution:
    def rob(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        if not nums:
            return 0


        n = len(nums)
        if n == 1:
            return nums[0]
        nums1 = nums[:n-1]
        nums2 = nums[1:]
        f1 = self.canDo(nums1)
        f2 = self.canDo(nums2)
        return max(f1,f2)

    def canDo(self, nums):        
        r = len(nums)
        ppre=pre=cur = 0

        for i in range(r):
            cur = max(pre,ppre+nums[i])
            ppre,pre = pre,cur

        return cur