2023.03

challenges/2023/03-gearRatios/README.md

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+# [Day 3: Gear Ratios](https://adventofcode.com/2023/day/3)

challenges/2023/03-gearRatios/main.py

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+import os
+import sys
+
+
+def _debug(*args, **kwargs):
+    kwargs["file"] = sys.stderr
+    print(*args, **kwargs)
+
+
+Coordinate = tuple[int, int]
+Schematic = dict[Coordinate, str]
+
+
+def parse(instr: str) -> Schematic:
+    res = {}
+
+    lines = instr.splitlines()
+    max_x = len(lines[0])
+
+    for row_n, row in enumerate(lines):
+        assert len(row) == max_x
+        for col_n, char in enumerate(row):
+            res[(col_n, row_n)] = char
+
+    return res
+
+
+DIRECTIONS = [(-1, -1), (0, -1), (1, -1), (-1, 0), (1, 0), (-1, 1), (0, 1), (1, 1)]
+
+
+def apply_coord_delta(c: Coordinate, d: Coordinate) -> Coordinate:
+    a, b = c
+    e, f = d
+    return a + e, b + f
+
+
+def seek_digits(
+    sc: Schematic, start: Coordinate, delta: Coordinate
+) -> tuple[str, set[Coordinate]]:
+    digits = ""
+    coords = set()
+
+    cursor = start
+    while True:
+        cursor = apply_coord_delta(cursor, delta)
+        val = sc.get(cursor, ".")
+        if not val.isdigit():
+            break
+        coords.add(cursor)
+        digits += val
+
+    return digits, coords
+
+
+def collect_digits_around(
+    sc: Schematic, start: Coordinate
+) -> tuple[int, set[Coordinate]]:
+    backward_digits, backward_coords = seek_digits(sc, start, (-1, 0))
+    forward_digits, forward_coords = seek_digits(sc, start, (1, 0))
+
+    return (
+        int("".join(reversed(backward_digits)) + sc[start] + forward_digits),
+        backward_coords | forward_coords | set((start,)),
+    )
+
+
+def one(inp: str):
+    schematic = parse(inp)
+
+    consumed_numbers = set()
+    acc = 0
+
+    for coord in schematic:
+        if coord in consumed_numbers:
+            continue
+
+        char = schematic[coord]
+
+        if not char.isdigit():
+            continue
+
+        is_part_number = False
+        for delta in DIRECTIONS:
+            target = schematic.get(apply_coord_delta(coord, delta), ".")
+            if not (target.isdigit() or target == "."):
+                is_part_number = True
+                break
+
+        if is_part_number:
+            n, used_coords = collect_digits_around(schematic, coord)
+            consumed_numbers = consumed_numbers | used_coords
+            acc += int(n)
+
+    return acc
+
+
+def two(inp: str):
+    schematic = parse(inp)
+    acc = 0
+
+    for coord in schematic:
+        char = schematic[coord]
+
+        if char != "*":
+            continue
+
+        consumed_numbers = set()
+        numbers = []
+
+        for delta in DIRECTIONS:
+            test_coord = apply_coord_delta(coord, delta)
+            if test_coord in consumed_numbers:
+                continue
+            if schematic.get(test_coord, ".").isdigit():
+                n, c = collect_digits_around(schematic, test_coord)
+                consumed_numbers = consumed_numbers | c
+                numbers.append(n)
+
+        if len(numbers) == 2:
+            # is gear!
+            x, y = numbers
+            acc += x * y
+
+    return acc
+
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2 or sys.argv[1] not in ["1", "2"]:
+        print("Missing day argument", file=sys.stderr)
+        os.exit(1)
+    inp = sys.stdin.read().strip()
+    if sys.argv[1] == "1":
+        print(one(inp))
+    else:
+        print(two(inp))

challenges/2023/03-gearRatios/tests.json

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+{
+    "1": [
+        {"res": "4361", "in": "467..114..\n...*......\n..35..633.\n......#...\n617*......\n.....+.58.\n..592.....\n......755.\n...$.*....\n.664.598.."}
+    ],
+    "2": [
+        {"res": "467835", "in": "467..114..\n...*......\n..35..633.\n......#...\n617*......\n.....+.58.\n..592.....\n......755.\n...$.*....\n.664.598.."}
+    ]
+}