feat: add leetcode75/day28_152.py

feat: add leetcode75/day28_152.py

Author: hj.tian

leetcode75/day28_152.py

@@ -0,0 +1,83 @@
+from typing import List
+
+
+class Solution:
+ def maxProduct(self, nums: List[int]) -> int:
+ """
+ 状态压缩
+ """
+ if len(nums) < 1:
+ raise KeyError
+ maxs = dp_maxs = dp_mins = nums[0]
+ for i in range(1, len(nums)):
+ pre_dp_maxs = dp_maxs
+ dp_maxs = max(dp_maxs * nums[i], dp_mins * nums[i], nums[i])
+ # notes, 使用上次的 dp_maxs, 而非刚计算出来的
+ dp_mins = min(pre_dp_maxs * nums[i], dp_mins * nums[i], nums[i])
+ maxs = max(maxs, dp_maxs)
+ return maxs
+
+
+# class Solution:
+# def maxProduct(self, nums: List[int]) -> int:
+# """
+
+# -2 (-2)
+# 3 (3, -6)
+# 2 (2, 6, -12)
+# -1 (-1, -2, -6, 12)
+# 7 (7, -7, -14, -42, 84)
+# => 84
+# 如何求最大乘积， 正*正，负*负
+# max min
+# -2 (,,2) -2 (-2) -2 (-2)
+# 3 (-6,-6,3) 3 (3) -6 (-2,3)
+# 2 (6,-12,2) 6 (3,2) -12(-2,3,2)
+# -1 (-6,12,-1) 12 (-2,3,2,-1) -6 (3,2,-1)
+# 7 (84,-42,7) 84 (-2,3,2,-1,7) -42(3,2,-1,7)
+# => 84
+# dp_maxs[i]: 到数据i所构成连续子数据的最大乘积
+# dp_mins[i]: 到数据i所构成连续子数据的最小乘积
+# dp_maxs[i] = max(dp_maxs[i-1]*nums[i], dp_mins[i-1]*nums[i], nums[i])
+# dp_mins[i] = min(dp_maxs[i-1]*nums[i], dp_mins[i-1]*nums[i], nums[i])
+# max(dp_maxs)
+# """
+# if len(nums) < 1:
+# raise KeyError
+# dp_maxs = [0 for _ in nums]
+# dp_mins = [0 for _ in nums]
+# dp_maxs[0] = dp_mins[0] = nums[0]
+# for i in range(1, len(nums)):
+# dp_maxs[i] = max(dp_maxs[i - 1] * nums[i], dp_mins[i - 1] * nums[i], nums[i])
+# dp_mins[i] = min(dp_maxs[i - 1] * nums[i], dp_mins[i - 1] * nums[i], nums[i])
+# return max(dp_maxs)
+
+
+# class Solution:
+# def maxProduct(self, nums: List[int]) -> int:
+# """
+# -2 (-2)
+# 3 (3, -6)
+# 2 (2, 6, -12)
+# -1 (-1, -2, -6, 12)
+# 7 (7, -7, -14, -42, 84)
+# => 84
+# """
+# if len(nums) < 1:
+# raise KeyError
+# maxs = nums[0]
+# starts = set([nums[0]])
+# for num in nums[1:]:
+# next_starts = set([num])
+# for start in starts:
+# next_starts.add(num * start)
+# maxs = max(*next_starts, maxs)
+# starts = next_starts
+# return maxs
+
+
+if __name__ == "__main__":
+ assert Solution().maxProduct(nums=[2, 3, -2, 4]) == 6
+ assert Solution().maxProduct(nums=[-2, 0, -1]) == 0
+ assert Solution().maxProduct(nums=[-2, 3, 2, -1, 7]) == 84
+ assert Solution().maxProduct(nums=[-3, -4, -2]) == 12