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Is the sum of two even numbers even or odd? How about two odd numbers? One odd number and one even number?
If there is an even number of odd numbers, the sum will be even and vice versa.
Create an integer array to store all the even numbers in nums and another array to store all the odd numbers in nums. Sort both arrays.
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Yes, variations of this problem appear in coding interviews because it tests greedy thinking, parity reasoning, and careful edge-case handling. Companies often use similar problems to evaluate problem-solving with arrays and sorting.
Sorting helps quickly identify the largest k elements, which maximizes the initial subsequence sum. It also makes it easier to locate candidate elements for swapping when you need to fix the parity of the sum.
The optimal approach combines sorting and greedy selection. First choose the k largest elements to maximize the sum, then adjust parity if the sum is odd by swapping elements between the selected and unselected groups. This ensures the final sum is even while remaining as large as possible.
Most solutions rely on arrays combined with sorting. Since the problem mainly requires selecting elements and checking parity, no complex data structures are necessary beyond standard array operations.