From ed395fe7a7fd68f6db4ea94de8fdcdcb0fac5179 Mon Sep 17 00:00:00 2001
From: bthink <bthink@fake.com>
Date: Sun, 7 Dec 2025 15:59:37 +0100
Subject: first week of AOC 2025

---
 2025/aoc2025-d07.py | 56 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 56 insertions(+)
 create mode 100644 2025/aoc2025-d07.py

(limited to '2025/aoc2025-d07.py')

diff --git a/2025/aoc2025-d07.py b/2025/aoc2025-d07.py
new file mode 100644
index 0000000..e72effe
--- /dev/null
+++ b/2025/aoc2025-d07.py
@@ -0,0 +1,56 @@
+#advent of code 2025
+#day 07
+part1=0;
+part2=0;
+#parsing
+grid=dict();
+Ymax=0;
+Xmax=0;
+PuzzleInput=open("07.in","r");
+for y,line in enumerate(PuzzleInput):
+	Ymax+=1;
+	for x,c in enumerate(line.replace("\n","")):
+		grid[(x,y)]=c;
+		Xmax=max(Xmax,x+1);
+		if c=="S":
+			Start=(x,y); 
+			grid[(x,y)]=".";
+PuzzleInput.close();
+#solution
+total=(0,0);
+pathing=dict();
+pathing[total]=set();
+hitBottom=dict();
+splitters=set(); #encountered splitters
+beams=set([(Start,total)]);
+#recursive search
+def findTimelines(point):
+	if point in hitBottom:
+		return hitBottom[point];
+	hitBottom[point]=0;
+	for path in pathing[point]:
+		hitBottom[point]+=findTimelines(path);
+	return hitBottom[point];
+
+for step in range(0,Ymax+1,2): #every 2nd line is empty so i'm skipping it
+	newbeams=set();
+	while beams:
+		b,prev=beams.pop();
+		pathing[prev].add(b);
+		if b not in pathing: pathing[b]=set();
+		bx,by=b;
+		beam=(bx,by+2);
+		if grid.get(beam,".")=="^":
+			splitters.add(beam);
+			newbeams.add(((bx+1,by+2),(bx,by)));
+			newbeams.add(((bx-1,by+2),(bx,by)));
+		else:
+			newbeams.add(((bx,by+2),(bx,by)));
+		if by+2>Ymax and b not in hitBottom: 
+			hitBottom[b]=1; #register from which points beams hit the bottom
+	beams=newbeams;
+
+part1=len(splitters);
+part2=findTimelines(Start);
+print("part 1",part1,part1==1533);
+print("part 2",part2,part2==10733529153890);
-- 
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