Add day07, 2025

Author: snhansen

2025/day07/solution.py

@@ -0,0 +1,50 @@
+from functools import cache
+
+with open("input") as f:
+    inp = f.read().strip().split("\n")
+
+
+splitters = set()
+for y, line in enumerate(inp):
+    for x, c in enumerate(line):
+        if c == "^":
+            splitters.add(x + y*1j)
+        elif c == "S":
+            start = x + y*1j
+
+
+# Part 1
+cur = [start]
+beam = set()
+splitters_hit = set()
+while cur:
+    p = cur.pop(0)
+    if p in beam:
+        continue
+    beam.add(p)
+    p += 1j
+    if p.imag > len(inp):
+        continue
+    elif p in splitters:
+        cur.append(p - 1)
+        cur.append(p + 1)
+        splitters_hit.add(p)
+    else:
+        cur.append(p)
+
+print(len(splitters_hit))
+
+
+# Part 2
+@cache
+def no_timelines(p):
+    if p.imag > len(inp):
+        return 1
+    p += 1j
+    if p in splitters:
+        return no_timelines(p + 1) + no_timelines(p - 1)
+    else:
+        return no_timelines(p)
+
+
+print(no_timelines(start))