Day 7: Bridge Repair

README.md

@@ -11,4 +11,4 @@ Development occurs in language-specific directories:
 |[Day4.hs](hs/src/Day4.hs)|[Day4.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day4.kt)|[day4.py](py/aoc2024/day4.py)|[day4.rs](rs/src/day4.rs)|
 |[Day5.hs](hs/src/Day5.hs)|[Day5.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day5.kt)|[day5.py](py/aoc2024/day5.py)|[day5.rs](rs/src/day5.rs)|
 |[Day6.hs](hs/src/Day6.hs)|[Day6.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day6.kt)|[day6.py](py/aoc2024/day6.py)|[day6.rs](rs/src/day6.rs)|
-|[Day7.hs](hs/src/Day7.hs)|[Day7.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day7.kt)|||
+|[Day7.hs](hs/src/Day7.hs)|[Day7.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day7.kt)|[day7.py](py/aoc2024/day7.py)||

py/aoc2024/day7.py

@@ -0,0 +1,76 @@
+"""
+Day 7:
+"""
+
+from typing import Callable, Iterable
+
+SAMPLE_INPUT = """
+190: 10 19
+3267: 81 40 27
+83: 17 5
+156: 15 6
+7290: 6 8 6 15
+161011: 16 10 13
+192: 17 8 14
+21037: 9 7 18 13
+292: 11 6 16 20
+"""
+
+
+def _solve(data: str, op: Callable[[int, int], Iterable[int]]) -> int:
+    total = 0
+    for line in filter(None, data.splitlines()):
+        lhs, rhs = line.split(":", maxsplit=1)
+        lhs, rhs = int(lhs), [int(value) for value in rhs.split()]
+
+        def ok(x, remaining):
+            y = remaining[-1]
+            return (
+                x == y
+                if len(remaining) == 1
+                else any(ok(z, remaining[:-1]) for z in op(x, y))
+            )
+
+        if ok(lhs, rhs):
+            total += lhs
+    return total
+
+
+def part1(data: str) -> int:
+    """
+    >>> part1(SAMPLE_INPUT)
+    3749
+    """
+
+    def op(x, y):
+        values = []
+        if x >= y:
+            values.append(x - y)
+        if not x % y:
+            values.append(x // y)
+        return values
+
+    return _solve(data, op)
+
+
+def part2(data: str) -> int:
+    """
+    >>> part2(SAMPLE_INPUT)
+    11387
+    """
+
+    def op(x, y):
+        values = []
+        if x >= y:
+            values.append(x - y)
+        if not x % y:
+            values.append(x // y)
+        x, y = str(x), str(y)
+        if x.endswith(y) and len(x) > len(y):
+            values.append(int(x[: -len(y)]))
+        return values
+
+    return _solve(data, op)
+
+
+parts = (part1, part2)

py/pyproject.toml

@@ -30,6 +30,7 @@ day3 = "aoc2024.day3:parts"
 day4 = "aoc2024.day4:parts"
 day5 = "aoc2024.day5:parts"
 day6 = "aoc2024.day6:parts"
+day7 = "aoc2024.day7:parts"
 
 [build-system]
 requires = ["poetry-core"]