Reference library

Lists & loops

Iterate, transform, and combine sequences with readable loop patterns.

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Lists & loops easy

How to Compute Sliding Window Sum of Size k in Python

Compute the sum of every contiguous subarray of a fixed size k using an efficient O(n) sliding window technique.

sliding-window list sum
Python 
def sliding_window_sum(nums, k):
    """Return a list of sums for each contiguous subarray of size k."""
    if not nums or k <= 0 or k > len(nums):
        return []
    
    result = []
    window_sum = sum(nums[:k])
    result.append(window_sum)
    
    for i in range(k, len(nums)):
        window_sum += nums[i] -…
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