day_39

198. 打家劫舍

class Solution:
    def rob(self, nums: List[int]) -> int:
        if len(nums) == 1:
            return nums[0]
        dp = [0] * len(nums)
        dp[0], dp[1] = nums[0], max(nums[0], nums[1])
        for i in range(2, len(nums)):
            dp[i] = max(dp[i - 1], dp[i - 2] + nums[i])
        return dp[len(nums) - 1]

213. 打家劫舍 II

class Solution:
    def rob(self, nums: List[int]) -> int:
        if len(nums) <= 2:
            return max(nums)
        def get_dp(nums):
            if len(nums) == 1:
                return nums[0]
            n = len(nums)
            dp = [0] * n
            dp[0], dp[1] = nums[0], max(nums[0], nums[1])
            for i in range(2, n):
                dp[i] = max(dp[i - 1], dp[i - 2] + nums[i])
            return dp[n - 1]
        return max(get_dp(nums[:-1]), get_dp(nums[1:]))

337. 打家劫舍 III

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right``
class Solution:
    def rob(self, root: Optional[TreeNode]) -> int:
        return max(self.traversal(root))
    def traversal(self, node):
            if not node:
                return (0, 0)
            left = self.traversal(node.left)
            right = self.traversal(node.right)
            val_0 = max(left) + max(right)
            val_1 = node.val + left[0] + right[0]
            return val_0, val_1

这题目自己想不出来，但是讲过之后，看了代码知道了意思，但是过一段时间，恐怕会忘。