Description
The window never changes size; you slide it and update by adding the new element / removing the one that fell off.
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Reach for when
Max sum of k consecutive elements, averages of subarrays of size k.
Runtime
O(n)
Visualization
Pseudocode
current = compute(l, r)
for r in range(k, length(array)):
l = r-k
remove l from current
add r to current
update answer
return answer
Code
def max_sum_k(arr, k):
window = sum(arr[:k])
best = window
for r in range(k, len(arr)):
window += arr[r]
window -= arr[r - k]
best = max(best, window)
return best