From 8d65bf401ae1870e22179b8fdcad61fb21eadaec Mon Sep 17 00:00:00 2001
From: Alex Karle <alex@alexkarle.com>
Date: Sat, 7 Dec 2024 02:50:30 +0100
Subject: [PATCH] 2024: Day 6 pt 2

I still feel like there's a smarter answer here, but this works!
---
 2024/06/1.py |  1 -
 2024/06/2.py | 88 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 88 insertions(+), 1 deletion(-)
 create mode 100755 2024/06/2.py

diff --git a/2024/06/1.py b/2024/06/1.py
index ecc34f7..78e0a69 100755
--- a/2024/06/1.py
+++ b/2024/06/1.py
@@ -65,7 +65,6 @@ if __name__ == '__main__':
 
     seen = set()
     while guard[0] is not None:
-        oldguard = guard
         seen.add(guard)
         guard, dir = move(G, guard, dir)
 
diff --git a/2024/06/2.py b/2024/06/2.py
new file mode 100755
index 0000000..8889491
--- /dev/null
+++ b/2024/06/2.py
@@ -0,0 +1,88 @@
+#!/usr/bin/env python3
+import sys
+
+def parse():
+    G = []
+    guard = (None, None)
+    r = 0
+    for l in sys.stdin:
+        G.append([x for x in l.strip()])
+        if "^" in l:
+            guard = (r, l.index("^"))
+        r += 1
+
+    if not guard[0]:
+        raise Exception("Unable to find Guard")
+
+    return G, guard
+
+def turn(dir):
+    if dir == "^":
+        return ">"
+    elif dir == ">":
+        return "v"
+    elif dir == "v":
+        return "<"
+    elif dir == "<":
+        return "^"
+    else:
+        raise Exception(f"Bad direction {dir}")
+
+def move(G, guard, dir):
+    if dir == "^":
+        next = (guard[0] - 1, guard[1])
+    elif dir == "v":
+        next = (guard[0] + 1, guard[1])
+    elif dir == ">":
+        next = (guard[0], guard[1] + 1)
+    elif dir == "<":
+        next = (guard[0], guard[1] - 1)
+    else:
+        raise Exception(f"Bad direction {dir}")
+
+    if next[0] >= len(G) or next[0] < 0 or next[1] >= len(G[0]) or next[1] < 0:
+        # off the map
+        return ((None, None), None)
+
+    if G[next[0]][next[1]] == "#":
+        dir = turn(dir)
+        return (guard, dir)
+
+    return (next, dir)
+
+def pprint(G, guard, dir):
+    for i in range(len(G)):
+        for j in range(len(G[0])):
+            if (i, j) == guard:
+                print(dir, end='')
+            else:
+                print(G[i][j], end='')
+        print("")
+
+def check(G, guard, dir):
+    seen = set()
+    while guard[0] is not None:
+        seen.add((guard, dir))
+        guard, dir = move(G, guard, dir)
+        if dir is None:
+            return seen
+        if (guard, dir) in seen:
+            return None
+
+if __name__ == '__main__':
+    G, guard = parse()
+    dir = "^"
+
+    regseen = check(G, guard, dir)
+    sq2chk = { x[0] for x in regseen if x[0] != guard }
+
+    c = 0
+    for sq in sq2chk:
+        print(sq)
+        i, j = sq
+        G[i][j] = '#'
+        if check(G, guard, dir) is None:
+            c += 1
+        G[i][j] = '.'
+
+    print(c)
--
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