Day 7

andreis · andreis · commit 7917c7aebb51 · 2025-12-07T23:01:50.000Z
diff --git a/2025/07.py b/2025/07.py
@@ -0,0 +1,40 @@
+from functools import cache, reduce
+from os import environ
+
+
+lines = open("07.sample.txt" if environ.get("DEBUG") else "07.txt").read().splitlines()
+
+
+def part1(lines):
+    def step(state, line):  # reducer a bit forced lol
+        beams, ans = state
+        hits = [i for i, c in enumerate(line) if c == "^" and beams[i]]
+        new_beams = beams[:]
+
+        for i in hits:
+            new_beams[i] = False
+            new_beams[i - 1] = new_beams[i + 1] = True
+
+        return new_beams, ans + len(hits)
+
+    return reduce(step, lines, ([c == "S" for c in lines[0]], 0))[1]
+
+
+def part2(lines):
+    splitter_rows = [line for line in lines if "^" in line]
+
+    @cache
+    def dfs(x, c):
+        if x == len(splitter_rows):
+            return 1
+        if not (0 <= c < len(lines[0])):
+            return 0
+        if splitter_rows[x][c] == "^":
+            return dfs(x + 1, c - 1) + dfs(x + 1, c + 1)
+        return dfs(x + 1, c)
+
+    return dfs(0, lines[0].index("S"))
+
+
+print(part1(lines))
+print(part2(lines))
