London | November 25 | Donara Blanc | Sprint 2 | Improve with caches#132
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donarbl wants to merge 1 commit intoCodeYourFuture:mainfrom
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London | November 25 | Donara Blanc | Sprint 2 | Improve with caches#132donarbl wants to merge 1 commit intoCodeYourFuture:mainfrom
donarbl wants to merge 1 commit intoCodeYourFuture:mainfrom
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donarbl
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📅 Sprint 2
cjyuan
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Mar 2, 2026
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10
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+26
| @@ -26,7 +19,12 @@ def ways_to_make_change_helper(total: int, coins: List[int]) -> int: | |||
| if total_from_coins == total: | |||
| ways += 1 | |||
| else: | |||
| intermediate = ways_to_make_change_helper(total - total_from_coins, coins=coins[coin_index+1:]) | |||
| intermediate = ways_to_make_change_helper( | |||
| total - total_from_coins, | |||
| coins=coins[coin_index + 1:], | |||
| cache=cache | |||
| ) | |||
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Tuple or array creation are relatively costly operations.
From lines 5 and 24, we know coins can only be one of the following 9 tuples:
(200, 100, 50, 20, 10, 5, 2, 1)
(100, 50, 20, 10, 5, 2, 1)
(50, 20, 10, 5, 2, 1)
...
(1)
()
We could further improve the performance if we can
- avoid repeatedly creating the same sub-tuples at line 24 (e.g. use another cache), and
- create key as (total, a_unique_integer_identifying_the_subtuple) instead of as (total, tuple of coins)
- There are only a small number of different sub-tuples. We can easily assign each sub-tuple a unique integer.
cjyuan
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Self checklist
Changelist
both functions now avoid redundant recursive calls