I often find myself having to reimplement the sliding window algorithm. Here is a basic template for sliding windows. It is a good starting point for adding other features like counting characters or tracking the largest size of the window.
This template takes a basic two-pointer approach. But it reads better from top to
bottom and generalizes more than other solutions I have seen. First we increase the window size by shifting the right pointer r.
If the window reaches the max size we slide it by incrementing pointer r and
the left pointer l. If we reach the right side we shrink the window by increasing
the left pointer l.
s = "ABCDEFG"
window_length = 3
l = r = 0
while l < len(s):
if r - l < window_length and r < len(s):
r += 1
elif r - l == window_length and r < len(s):
r += 1
l += 1
else:
l += 1
win = s[l:r]
print(win)output
A
AB
ABC
BCD
CDE
DEF
EFG
FG
GWe can rewrite this as a generator if you prefer
# sliding_window.py
def sliding_window_generator(s, window_length):
l = r = 0
while l < len(s):
if r - l < window_length and r < len(s):
r += 1
elif r - l == window_length and r < len(s):
r += 1
l += 1
else:
l += 1
win = s[l:r]
yield(win)interaction
$ python -i sliding_window.py
>>> g = sliding_window_generator('ABCDEFG', 3)
>>> next(g)
'A'
>>> print(next(g))
AB
>>> next(g)
'ABC'
>>> next(g)
'BCD'
>>> next(g)
'CDE'
>>> next(g)
'DEF'
>>> next(g)
'EFG'
>>> next(g)
'FG'
>>> next(g)
'G'If you need help solving your business problems with software read how to hire me.