Given an array of integers and a positive integer k, find the maximum sum of any contiguous subarray of size k.
For example, given nums = [2, 1, 5, 1, 3, 2] and k = 3, the output is 9 because the subarray [5, 1, 3] has the largest sum among all subarrays of size 3.
Explain your approach, why a sliding window is more efficient than brute force, and analyze the time and space complexity.
How to approach it
- Hint 1
A brute force approach recalculates the sum for every window from scratch. How much redundant work is that?
- Hint 2
When the window slides one position right, only one element enters and one element leaves.
- Hint 3
Maintain a running sum: add the new element entering the window and subtract the element leaving.
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