Maximum Sum Subarray of Size K

Problem Given an integer array and a window size k, find the maximum sum of any contiguous subarray of exactly length k.

Input / Output

• Input: int array nums, int k.
• Output: the maximum sum over all length-k windows.

Constraints

• 1 <= k <= n <= 10^5.
• Values may be negative. O(n) expected — recomputing each window sum is O(n*k).

Example

• [2,1,5,1,3,2], k=3 -> 9 (subarray [5,1,3]).
• [-1,-2,-3], k=2 -> -3 (subarray [-1,-2]).