Given a list of integers nums and a positive integer k, return a list containing the sum of every contiguous window of exactly k elements, from left to right. If k is larger than the list, return [].
Examples
Input: nums = [1, 2, 3, 4, 5], k = 3
Output: [6, 9, 12]
Explanation: 1+2+3, 2+3+4, 3+4+5.
Input: nums = [1, 2, 3], k = 4
Output: []
Constraints
0 <= len(nums) <= 10**51 <= k <= 10**5- Return a new list.
- Target: O(n) time; summing each window from scratch is too slow when k is large.
Goals
- Maintain a running window sum instead of re-summing each slice
- Return one value per window position
- Handle k larger than the list