213 House Robber II

https://leetcode.com/problems/house-robber-ii/

solution

• 首尾相连, 从整体上分两个状态来考虑

class Solution:
    def rob(self, nums: List[int]) -> int:
        if len(nums) == 0:
            return 0
        if len(nums) == 1:
            return nums[0]
        
        res1 = self._run_rob(nums, 0, len(nums)-2)
        res2 = self._run_rob(nums, 1, len(nums)-1)
        return max(res1, res2)

    def _run_rob(self, nums, start, end):  # 左闭右闭
        if end == start:
            return nums[start]
        
        pre = nums[start]
        cur = max(nums[start], nums[start+1])

        for i in range(start+2, end+1):
            tmp = cur
            cur = max(pre+nums[i], cur)
            pre = tmp
        return cur        

时间复杂度：O() 空间复杂度：O()