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AoC 2020: day9, refactored part2 with O(n) solution

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Signed-off-by: Ettore Dreucci <ettore.dreucci@gmail.com>
This commit is contained in:
Ettore Dreucci
2020-12-10 00:50:55 +01:00
parent c8a9f13402
commit 382030bdd3
2 changed files with 14 additions and 13 deletions
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21
2020-python/solutions/day_9.py
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@@ -48,16 +48,17 @@ def part1(entries: list, preamble_length: int) -> int:
def part2(entries: list, invalid_number: int) -> int:
"""part2 solver"""
for index, _ in enumerate(entries):
test_set = [entries[index]]
test_set_len = 1
while test_set_len < len(entries) - index:
test_set.append(entries[index+test_set_len])
test_set_len += 1
if sum(test_set) == invalid_number:
return min(test_set) + max(test_set)
return None
left, right = 0, 1
interval_sum = entries[left] + entries[right]
while True:
if interval_sum < invalid_number:
right += 1
interval_sum += entries[right]
elif interval_sum > invalid_number:
interval_sum -= entries[left]
left += 1
else:
return min(entries[left:right+1]) + max(entries[left:right+1])
def test_input_day_9():
"""pytest testing function"""