2025 07

Python/2025/07/main.py

@@ -0,0 +1,57 @@
+import bisect
+input = open("input", 'r')
+
+splitters = None
+start = None
+for row, line in enumerate(input):
+    if splitters == None:
+        splitters = [[] for _ in range(len(line))]
+    for col, char in enumerate(line):
+        if char == "S":
+            start = (row, col)
+        elif char == "^":
+            splitters[col].append(row)
+
+def beam_to_splitter(splitters, beam):
+    beam_row, beam_col = beam
+    splitters_in_col = splitters[beam_col]
+    next_splitter = bisect.bisect_right(splitters_in_col, beam_row)
+    if next_splitter == len(splitters_in_col):
+        return None
+    return (splitters_in_col[next_splitter], beam_col)
+
+def part1(splitters, start):
+    used_splitters = set()
+    unresolved_splitters = [beam_to_splitter(splitters,start)]
+    while unresolved_splitters:
+        splitter = unresolved_splitters.pop()
+        used_splitters.add(splitter)
+
+        splitter_row, splitter_col = splitter
+        for offset in [-1, 1]:
+            new_beam = (splitter_row, splitter_col+offset)
+            next_splitter = beam_to_splitter(splitters, new_beam)
+            if not next_splitter or next_splitter in used_splitters:
+                continue
+            unresolved_splitters.append(next_splitter)
+
+    return len(used_splitters)
+
+def part2(splitters, start):
+    splitter_multiverses = {}
+    def multiverse_count(splitters, splitter):
+        if splitter == None:
+            return 1
+        if splitter not in splitter_multiverses:
+            splitter_multiverses[splitter] = 0
+            splitter_row, splitter_col = splitter
+            for offset in [-1, 1]:
+                new_beam = (splitter_row, splitter_col+offset)
+                next_splitter = beam_to_splitter(splitters, new_beam)
+                splitter_multiverses[splitter] += multiverse_count(splitters, next_splitter)
+        return splitter_multiverses[splitter]
+
+    return multiverse_count(splitters, start)
+
+print(part1(splitters, start))
+print(part2(splitters, start))