Day 19: Aplenty

README.md

@@ -23,4 +23,4 @@ Development occurs in language-specific directories:
 |[Day16.hs](hs/src/Day16.hs)|[Day16.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day16.kt)|[day16.py](py/aoc2023/day16.py)|[day16.rs](rs/src/day16.rs)|
 |[Day17.hs](hs/src/Day17.hs)|[Day17.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day17.kt)|[day17.py](py/aoc2023/day17.py)|[day17.rs](rs/src/day17.rs)|
 |[Day18.hs](hs/src/Day18.hs)|[Day18.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day18.kt)|[day18.py](py/aoc2023/day18.py)|[day18.rs](rs/src/day18.rs)|
-|[Day19.hs](hs/src/Day19.hs)|[Day19.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day19.kt)|||
+|[Day19.hs](hs/src/Day19.hs)|[Day19.kt](kt/aoc2023-lib/src/commonMain/kotlin/com/github/ephemient/aoc2023/Day19.kt)|[day19.py](py/aoc2023/day19.py)||

py/aoc2023/day19.py

@@ -0,0 +1,122 @@
+"""
+Day 19: Aplenty
+"""
+
+from math import prod
+
+SAMPLE_INPUT = """
+px{a<2006:qkq,m>2090:A,rfg}
+pv{a>1716:R,A}
+lnx{m>1548:A,A}
+rfg{s<537:gd,x>2440:R,A}
+qs{s>3448:A,lnx}
+qkq{x<1416:A,crn}
+crn{x>2662:A,R}
+in{s<1351:px,qqz}
+qqz{s>2770:qs,m<1801:hdj,R}
+gd{a>3333:R,R}
+hdj{m>838:A,pv}
+
+{x=787,m=2655,a=1222,s=2876}
+{x=1679,m=44,a=2067,s=496}
+{x=2036,m=264,a=79,s=2244}
+{x=2461,m=1339,a=466,s=291}
+{x=2127,m=1623,a=2188,s=1013}
+"""
+
+
+def _parse_rules(data):
+    for line in data.splitlines():
+        if "{" not in line or not line.endswith("}"):
+            continue
+        yield line[: line.index("{")], [
+            (
+                rule[rule.index(":") + 1 :],
+                (rule[0], rule[1], int(rule[2 : rule.index(":")])),
+            )
+            if ":" in rule
+            else (rule, None)
+            for rule in line[line.index("{") + 1 : -1].split(",")
+        ]
+
+
+def _parse_points(data):
+    for line in data.splitlines():
+        if not line.startswith("{") or not line.endswith("}"):
+            continue
+        yield {kv[0]: int(kv[2:]) for kv in line[1:-1].split(",") if kv[1] == "="}
+
+
+def part1(data):
+    """
+    >>> part1(SAMPLE_INPUT)
+    19114
+    """
+    rules, points = data.split("\n\n", maxsplit=1)
+    rules = dict(_parse_rules(rules))
+    points = list(_parse_points(points))
+
+    acc = 0
+    for point in points:
+        name = "in"
+        while name in rules:
+            for name, comparison in rules[name]:
+                if not comparison:
+                    break
+                key, compare, value = comparison
+                if (
+                    compare == "<"
+                    and point[key] < value
+                    or compare == ">"
+                    and point[key] > value
+                ):
+                    break
+            else:
+                raise RuntimeError("unreachable")
+        if name == "A":
+            acc += sum(point.values())
+    return acc
+
+
+def part2(data):
+    """
+    >>> part2(SAMPLE_INPUT)
+    167409079868000
+    """
+    rules, _ = data.split("\n\n", maxsplit=1)
+    rules = dict(_parse_rules(rules))
+
+    def go(name, bounds):
+        if any(first > last for first, last in bounds.values()):
+            return 0
+        if name == "A":
+            return prod(last - first + 1 for first, last in bounds.values())
+        if name not in rules:
+            return 0
+        acc = 0
+        # pylint: disable=R1704
+        for name, comparison in rules[name]:
+            if not comparison:
+                acc += go(name, bounds)
+                break
+            key, compare, value = comparison
+            lo, hi = bounds[key]
+            match compare:
+                case "<":
+                    intersection = lo, min(hi, value - 1)
+                    difference = value, hi
+                case ">":
+                    intersection = max(lo, value + 1), hi
+                    difference = lo, min(hi, value)
+                case _:
+                    raise KeyError(compare)
+            if difference[0] > difference[1]:
+                break
+            acc += go(name, bounds | {key: intersection})
+            bounds[key] = difference
+        return acc
+
+    return go("in", {k: (1, 4000) for k in "xmas"})
+
+
+parts = (part1, part2)

py/pyproject.toml

@@ -40,6 +40,7 @@ day15 = "aoc2023.day15:parts"
 day16 = "aoc2023.day16:parts"
 day17 = "aoc2023.day17:parts"
 day18 = "aoc2023.day18:parts"
+day19 = "aoc2023.day19:parts"
 
 [tool.black]
 target_version = ["py312"]