MediumNo. 2036LeetCode Premium
Maximum Alternating Subarray Sum — LeetCode 2036 Python Solution
- Pattern
- Dynamic Programming
- Topics
- Array, Dynamic Programming
- Reading time
- 2 min
- Source
- leetcode.com
The problem
A subarray of a 0-indexed integer array is a contiguous non-empty sequence of elements within an array. The alternating subarray sum of a subarray that ranges from index i to j (inclusive, 0 <= i <= j < nums.length) is nums[i] - nums[i+1] + nums[i+2] - ...
Example
- Input
- nums = [3,-1,1,2]
- Output
- 5
- Explanation
- The subarray [3,-1,1] has the largest alternating subarray sum.
Python solution
class Solution:
def maximumAlternatingSubarraySum(self, nums: List[int]) -> int:
ans = f = g = -inf
for x in nums:
f, g = max(g, 0) + x, f - x
ans = max(ans, f, g)
return ansComplexity
- Time
- O(n)where n is the length of the array nums
- Space · auxiliary
- O(1)
Pattern: Dynamic Programming
Define a state, write the transition, and stop recomputing the same subproblem. LeetCode 2036. Maximum Alternating Subarray Sum is filed here on both counts: the reference solution below belongs to the algorithm family this hub collects, and LeetCode tags it Dynamic Programming.
The dynamic programming guide has the Python template for the pattern and the 481 LeetCode problems that use it.
Related problems
| No. | Problem | Difficulty |
|---|---|---|
| 0045 | Jump Game II | Medium |
| 0053 | Maximum Subarray | Medium |
| 0055 | Jump Game | Medium |
| 0063 | Unique Paths II | Medium |
| 0064 | Minimum Path Sum | Medium |
| 0085 | Maximal Rectangle | Hard |
Frequently asked questions
- How hard is LeetCode 2036. Maximum Alternating Subarray Sum?
LeetCode 2036. Maximum Alternating Subarray Sum is rated Medium on LeetCode.
- What is the time complexity of LeetCode 2036. Maximum Alternating Subarray Sum?
The Python solution on this page runs in O(n), where n is the length of the array nums.
- What is the space complexity of LeetCode 2036. Maximum Alternating Subarray Sum?
The Python solution on this page uses O(1) auxiliary space.
- What topics does LeetCode 2036. Maximum Alternating Subarray Sum cover?
LeetCode 2036. Maximum Alternating Subarray Sum is tagged Array and Dynamic Programming on LeetCode.
- Is LeetCode 2036. Maximum Alternating Subarray Sum a premium problem?
Yes. LeetCode 2036. Maximum Alternating Subarray Sum is a LeetCode Premium problem, so the full statement and test cases require a paid LeetCode subscription.