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)