commit 1cdb49fe5bab260c9e2ca565f0b03a9a8eecac16 (patch)
parent 12204b1a35de45a1388599afe5608ec3cc37af35
Author: Alex Karle <alex@alexkarle.com>
Date: Tue, 3 Dec 2024 02:44:10 +0100
2024: Golf day 2 pt 2 a bit
I'm fairly convinced this is true in the general case?
Diffstat:
1 file changed, 19 insertions(+), 19 deletions(-)
diff --git a/2024/02/2.py b/2024/02/2.py
@@ -1,38 +1,38 @@
import sys
-def is_safe(report):
+def bad_level(report):
delta = None
prev = None
safe = True
- for n in report:
+ for i in range(len(report)):
+ n = report[i]
if prev:
d2 = n - prev
if not delta:
delta = d2
if abs(d2) > 3 or d2 == 0 or (delta and delta * d2 < 0):
- safe = False
- break
+ return i
prev = n
- return safe
+ return -1
total = 0
for l in sys.stdin:
report = [int(x) for x in l.split()]
+ t = total
- safe = is_safe(report)
- if not safe:
- # feels like there should be a faster method than brute forcing
- # every combination? Escaping me right now.
- # The catch is that in cases like 1 3 2 3 4, we want to drop
- # the first 3, but it doesn't _look_ bad until we see the 2.
- # When we see the bad 2, we would have to try to drop the 2
- for i in range(len(report)):
- subrep = [report[j] for j in range(len(report)) if j != i]
- safe = is_safe(subrep)
- if safe:
- break
-
- if safe:
+ bad = bad_level(report)
+ if bad == -1:
total += 1
+ else:
+ # it could be that the bad index is any of:
+ # - the result returned by bad_level (1 10 2 3) -- bad causes spike
+ # - the index before that (bad - 1) (10 1 2 3) -- prev bad causes spike
+ # - the index before that (bad - 2) (1 2 1 0) -- sign change
+ for i in [0, 1, 2]:
+ if bad - i >= 0:
+ subrep = [report[j] for j in range(len(report)) if j != bad - i]
+ if bad_level(subrep) == -1:
+ total += 1
+ break
print(total)
