动态规划_leetcode213

class Solution(object):
    def rob(self, nums):
        """
 :type nums: List[int]
 :rtype: int
 """


 if not nums:
 return 0

 length = len(nums)

 if length == 1:
 return nums[0]
 if length == 2:
 return max(nums[0],nums[1])
 if length == 3:
 return max(nums[0],nums[1],nums[2])


 # memo[i]考虑偷 nums[i,n]的箱子
 memo = [-1 for i in range(length)]

 memo[length-1] = nums[length-1]

 for i in range(length-2,0,-1):
 for j in range(i,length):

 if j+2 < length:
 memo[i] = max(memo[i],nums[j] + memo[j+2])
 else:
 memo[i] = max(memo[i],nums[j])



 # 原问题分解为 偷两边 比较 memo[1] 和 memo[0] 的最优值
 # 注意 memo[1] 的范围是 nums[1,n-1]
 # memo[0] 的范围是 nums[2,n-2]
 validValue = memo[1]

 for i in range(length):

 memo[i] = -1

 memo[length-2] = nums[length-2]

 for i in range(length-3,-1,-1):
 for j in range(i,length-1):
 if j+2 < length-1:
 memo[i] = max(memo[i],nums[j] + memo[j+2])
 else:
 memo[i] = max(memo[i],nums[j])


 return max(memo[0],validValue)


s = Solution()

# nm = [1,2,3,1]
nm = [8,2,8,9,2]

print s.rob(nm)