198. House Robber
https://leetcode.com/problems/house-robber/
solution
只用到两个状态的DP,可以进一步优化空间
class Solution:
def rob(self, nums: List[int]) -> int:
if len(nums) <= 2:
return max(nums)
dp = [0] * len(nums)
dp[0] = nums[0]
dp[1] = 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[-1]
时间复杂度:O(n) 空间复杂度:O(n)
follow up
树形DP
此外,还有三角形DP 120. Triangle
class Solution:
def rob(self, root: Optional[TreeNode]) -> int:
dp = self.traversal(root)
return max(dp)
def traversal(self, root):
if not root:
return (0, 0)
l = self.traversal(root.left)
r = self.traversal(root.right)
val0 = max(l[0], l[1]) + max(r[0], r[1]) # 不偷当前节点
val1 = root.val + l[0] + r[0] # 偷当前节点
return [val0, val1]
时间复杂度:O() 空间复杂度:O()
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