Solve 2019:03 "Crossed Wires"

2019-python/output/day_03.py

@@ -0,0 +1,66 @@
+from collections import defaultdict
+from output import answer, puzzleinput
+
+n = 3
+title = "Crossed Wires"
+
+directions = {
+    "U": (-1, 0),
+    "R": (0, 1),
+    "D": (1, 0),
+    "L": (0, -1),
+}
+
+
+@puzzleinput(n)
+def parse_input(data):
+    return [line.split(",") for line in data.split()]
+
+
+@answer(
+    1, "As the crow flies, closest intersection Manhattan distance is {} units away"
+)
+def part_1(wires):
+    def follow(instructions):
+        seen = []
+        pos = (0, 0)
+        for instruction in instructions:
+            urdl, *l = instruction
+            distance = int("".join(l))
+            for _ in range(distance):
+                pos = (pos[0] + directions[urdl][0], pos[1] + directions[urdl][1])
+                seen.append(pos)
+        return set(seen)
+
+    wa = follow(wires[0])
+    wb = follow(wires[1])
+
+    return min(sum(map(abs, i)) for i in wa & wb)
+
+
+@answer(2, "By travel, closest intersection Manhattan distance is {} units away")
+def part_2(wires):
+    seen = defaultdict(dict)
+
+    def follow(instructions, i):
+        steps = 0
+        pos = (0, 0)
+        for instruction in instructions:
+            urdl, *l = instruction
+            distance = int("".join(l))
+            for _ in range(distance):
+                steps += 1
+                pos = (pos[0] + directions[urdl][0], pos[1] + directions[urdl][1])
+                if i not in seen[pos]:
+                    seen[pos][i] = steps
+
+    for i, wire in enumerate(wires):
+        follow(wire, i)
+
+    return min(sum(v.values()) for v in seen.values() if len(v) > 1)
+
+
+if __name__ == "__main__":
+    parsed = parse_input()
+    part_1(parsed)
+    part_2(parsed)