Pretty much just sort descending and sum the first k elements.
Clarify that the problem asks for the maximum sum of at most k elements from the array. Since all elements can be chosen if they are positive, the optimal strategy is to sort the array in descending order and sum the first k elements, but if there are fewer than k positive elements, sum only the positive ones. Alternatively, use a min-heap of size k to track the largest k elements, but sorting is simpler and efficient enough for most cases.
Pro tip: Always discuss edge cases like k=0, k >= array length, and arrays with negative numbers. Mention that if the array contains negative scores, we should only include positive ones up to k, and if all are negative, the maximum sum might be 0 (by choosing no elements) or the least negative if at least one must be chosen—clarify with the interviewer.
Confirm whether 'at most k' means we can choose fewer than k elements, and whether the array can contain negative numbers. Ask if we must choose exactly k or if zero elements is allowed.
Recognize that to maximize the sum, we should pick the largest positive numbers. If all numbers are negative, picking none yields 0, which is better than any negative sum.
Sort the array in descending order and sum the first k elements, but only if they are positive. Alternatively, use a min-heap of size k to find the k largest elements in O(n log k) time.
Consider cases where k=0 (return 0), k >= n (sum all positive elements), and arrays with all negatives (return 0 if allowed, else the maximum element).
State time and space complexity: sorting takes O(n log n), heap takes O(n log k). Walk through a few examples to verify correctness.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.