aoc

commit aa7ddad8c6949b5dfb7a4c77b49c5e65ae5aa782
parent be683b101393d3566261c9cc10351398bd2e1b6c
Author: Sebastiano Tronto <sebastiano@tronto.net>
Date:   Sun,  7 Dec 2025 06:34:41 +0100

Day 7 2025

Diffstat:
M
2025/07/a.py
 | 
17
+++++++++++++++--
A
2025/07/b.py
 | 
15
+++++++++++++++
M
2025/README.md
 | 
11
+++++++++++
M
README.md
 | 
2
+-

4 files changed, 42 insertions(+), 3 deletions(-)
diff --git a/2025/07/a.py b/2025/07/a.py
@@ -1,6 +1,19 @@
 import fileinput
 
 with fileinput.input() as lines:
-	for line in lines:
-		...
+	rows = [line[:-1] for line in lines]
+	pos = [rows[0].find('S')]
 
+s = 0
+for row in rows[1:]:
+	newpos = set()
+	for p in pos:
+		if row[p] == '^':
+			s += 1
+			newpos.add(p-1)
+			newpos.add(p+1)
+		else:
+			newpos.add(p)
+	pos = list(newpos)
+
+print(s)
diff --git a/2025/07/b.py b/2025/07/b.py
@@ -0,0 +1,15 @@
+import fileinput
+
+with fileinput.input() as lines:
+	rows = [line[:-1] for line in lines]
+	pos = {rows[0].find('S'): 1}
+
+for row in rows[1:]:
+	newpos = {}
+	for p, w in pos.items():
+		for pp in [p-1,p+1] if row[p] == '^' else [p]:
+			t = newpos.get(pp, 0)
+			newpos[pp] = t + w
+	pos = dict(newpos)
+
+print(sum(pos.values()))
diff --git a/2025/README.md b/2025/README.md
@@ -11,6 +11,7 @@ Example
 
 ```
 Day   -Part 1-   -Part 2-
+  7   00:05:27   00:20:40
   6   00:13:38   01:49:24
   5   00:04:39   00:22:19
   4   00:25:36   00:27:49
@@ -85,3 +86,13 @@ smart, very accomplishment.
 
 This year so far the only problems that took me more than 30 minutes
 are this and the first one, not exactly the hardest problems imaginable.
+
+### Day 7: Laboratories
+
+This was quite fun! For part 1, I iterate over the rows of the diagram
+keeping a list of the position currently occupied by a tachyon. I use a
+Python set to avoid duplicates. Part 2 is very similar, but the set is
+changed to a map where the keys are the positions and the values are the
+number of multiverses where a tachyon is in that position.  To update
+this value for the current row, I sum the values of all tachyons that
+end there from the previous row (that can be one or two tachyons).
diff --git a/README.md b/README.md
@@ -14,4 +14,4 @@ See `year/README.md` for instructions on how to run my code.
 |2022|  50 | Rust   | Done in 2025 to learn Rust |
 |2023|  50 | C      | All solved by December 25, 2023 |
 |2024|  50 | C++    | Each solved within 24h |
-|2025|  12 | Python | Work in progress... |
+|2025|  14 | Python | Work in progress... |