From a9e7decf71112190324d86be8980bef68c996b3c Mon Sep 17 00:00:00 2001
From: Armin Friedl <dev@friedl.net>
Date: Sun, 8 Dec 2024 11:40:32 +0100
Subject: [PATCH] Day08

---
 day08.py | 104 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 104 insertions(+)
 create mode 100644 day08.py

diff --git a/day08.py b/day08.py
new file mode 100644
index 0000000..a15812a
--- /dev/null
+++ b/day08.py
@@ -0,0 +1,104 @@
+#!/usr/bin/env python3
+
+#      N
+#   NW   NO
+# W    X    O
+#   SW   SO
+#      S
+
+from collections import defaultdict
+import math
+
+freqmap = defaultdict(list)
+lx = 0
+ly = 0
+
+with open("day08") as f:
+    for y,l in enumerate(f):
+        ly += 1
+        lx = len(l.strip())
+        for x,c in enumerate(l.strip()):
+            if c != '.':
+                freqmap[c].append((y,x))
+
+antinodes = set()
+
+for (_, coords) in freqmap.items():
+    for s,a in enumerate(coords):
+        for b in coords[s+1:]:
+            dy = abs(a[0]-b[0])
+            dx = abs(a[1]-b[1])
+
+            # vertical
+            if a[1]==b[1] and a[0]<b[0]:
+                    antinodes.add((a[0]-dy,a[1]))
+                    antinodes.add((b[0]+dy,b[1]))
+            if a[1]==b[1] and a[0]>b[0]:
+                    antinodes.add((a[0]+dy,a[1]))
+                    antinodes.add((b[0]-dy,b[1]))
+
+            # horizontal
+            if a[0]==b[0] and a[1]<b[1]:
+                    antinodes.add((a[0],a[1]-dx))
+                    antinodes.add((b[0],b[1]+dx))
+            if a[0]==b[0] and a[1]>b[1]:
+                    antinodes.add((a[0],a[1]+dx))
+                    antinodes.add((b[0],b[1]-dx))
+
+            # positive slope
+            if a[0]<b[0] and a[1]<b[1]:
+                antinodes.add((a[0]-dy,a[1]-dx))
+                antinodes.add((b[0]+dy,b[1]+dx))
+            if a[0]>b[0] and a[1]>b[1]:
+                antinodes.add((a[0]+dy,a[1]+dx))
+                antinodes.add((b[0]-dy,b[1]-dx))
+
+            # negative slope
+            if a[0]<b[0] and a[1]>b[1]:
+                antinodes.add((a[0]-dy,a[1]+dx))
+                antinodes.add((b[0]+dy,b[1]-dx))
+            if a[0]>b[0] and a[1]<b[1]:
+                antinodes.add((a[0]+dy,a[1]-dx))
+                antinodes.add((b[0]-dy,b[1]+dx))
+
+
+def boundscheck(antinode):
+    if antinode[0] < 0: return False
+    if antinode[0] >= ly: return False
+    if antinode[1] < 0: return False
+    if antinode[1] >= lx: return False
+
+    return True
+
+def printmap():
+    with open("day08") as f:
+        for y,l in enumerate(f):
+            for x,c in enumerate(l):
+                if c == '.':
+                    if (y,x) in antinodes2:
+                        print("#", end=" ")
+                    else: print(".", end=" ")
+                else:
+                    print(c.strip(), end=" ")
+            print()
+
+res = len({antinode for antinode in antinodes if boundscheck(antinode)})
+
+# 2
+
+antinodes2 = set()
+
+for (_, coords) in freqmap.items():
+    for s,a in enumerate(coords):
+        for b in coords[s+1:]:
+            slope = ((a[0]-b[0]) / (a[1]-b[1]))
+            # y = mx + y0
+            y0 = a[0] - slope*a[1]
+
+            for x in range(lx):
+                y = (slope*x)+y0
+                if abs(round(y)-y) < 0.0001:
+                    antinodes2.add((int(round(y)), x))
+
+
+res2 = len({antinode for antinode in antinodes2 if boundscheck(antinode)})