LeetCode 2036: Maximum Alternating Subarray Sum Solution

Master LeetCode problem 2036 (Maximum Alternating Subarray Sum), a medium challenge, with our optimized solutions in Java, C++, and Python. Explore detailed explanations, test your code in our interactive editor, and prepare for coding interviews.

2036. Maximum Alternating Subarray Sum

Medium

Array Dynamic Programming

Problem Explanation

Explanation:

To solve this problem, we can use dynamic programming. We will iterate through the array and keep track of the maximum alternating subarray sum ending at each position. At each index, we will consider two cases: either including the current element in the subarray or excluding it. We will update the maximum alternating subarray sum accordingly.

Here are the steps:

Initialize two variables maxEven and maxOdd to track the maximum alternating subarray sum ending at the current index for even and odd lengths respectively.
Iterate through the array and update maxEven and maxOdd based on the current element and the previous values.
The final answer will be the maximum of maxEven and maxOdd.

Time Complexity: O(N), where N is the number of elements in the input array. Space Complexity: O(1) as we are using only a constant amount of extra space.

Solution Code

class Solution {
    public long maxAlternatingSum(int[] nums) {
        long maxEven = 0, maxOdd = 0;
        for (int num : nums) {
            long newMaxEven = Math.max(maxOdd + num, maxEven);
            long newMaxOdd = Math.max(maxEven - num, maxOdd);
            maxEven = newMaxEven;
            maxOdd = newMaxOdd;
        }
        return Math.max(maxEven, maxOdd);
    }
}

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