Day 4: Ceres Search

README.md

@@ -8,4 +8,4 @@ Development occurs in language-specific directories:
 |[Day1.hs](hs/src/Day1.hs)|[Day1.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day1.kt)|[day1.py](py/aoc2024/day1.py)|[day1.rs](rs/src/day1.rs)|
 |[Day2.hs](hs/src/Day2.hs)|[Day2.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day2.kt)|[day2.py](py/aoc2024/day2.py)|[day2.rs](rs/src/day2.rs)|
 |[Day3.hs](hs/src/Day3.hs)|[Day3.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day3.kt)|[day3.py](py/aoc2024/day3.py)|[day3.rs](rs/src/day3.rs)|
-|[Day4.hs](hs/src/Day4.hs)|[Day4.kt](kt/aoc2024-lib/src/commonMain/kotlin/com/github/ephemient/aoc2024/Day4.kt)|||
+|[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)||

py/aoc2024/day4.py

@@ -0,0 +1,52 @@
+"""
+Day 4: Ceres Search
+"""
+
+SAMPLE_INPUT = """
+MMMSXXMASM
+MSAMXMSMSA
+AMXSXMAAMM
+MSAMASMSMX
+XMASAMXAMM
+XXAMMXXAMA
+SMSMSASXSS
+SAXAMASAAA
+MAMMMXMMMM
+MXMXAXMASX
+"""
+
+
+def part1(data: str) -> int:
+    """
+    >>> part1(SAMPLE_INPUT)
+    18
+    """
+    lines = data.splitlines()
+    return sum(
+        all(
+            (y2 := y + i * dy) in range(len(lines))
+            and (x2 := x + i * dx) in range(len(lines[y2]))
+            and lines[y2][x2] == c
+            for i, c in enumerate("XMAS")
+        )
+        for y, line in enumerate(lines)
+        for x in range(len(line))
+        for dx in range(-1, 2)
+        for dy in range(-1, 2)
+    )
+
+
+def part2(data: str) -> int:
+    """
+    >>> part2(SAMPLE_INPUT)
+    9
+    """
+    lines = data.splitlines()
+    return sum(
+        "".join(chars) in ("MMASS", "MSAMS", "SMASM", "SSAMM")
+        for above, line, below in zip(lines, lines[1:], lines[2:])
+        for chars in zip(above, above[2:], line[1:], below, below[2:])
+    )
+
+
+parts = (part1, part2)

py/pyproject.toml

@@ -27,6 +27,7 @@ aoc2024 = "aoc2024.main:main"
 day1 = "aoc2024.day1:parts"
 day2 = "aoc2024.day2:parts"
 day3 = "aoc2024.day3:parts"
+day4 = "aoc2024.day4:parts"
 
 [build-system]
 requires = ["poetry-core"]