2021 Day 03

2021/03/code.py

@@ -0,0 +1,37 @@
+# SPDX-License-Identifier: MIT
+# Copyright (c) 2021 Akumatic
+#
+# https://adventofcode.com/2021/day/03
+
+def read_file() -> list:
+    with open(f"{__file__.rstrip('code.py')}input.txt", "r") as f:
+        return [line for line in f.read().strip().split("\n")]
+
+def get_mcb(vals: list) -> list:
+    bit_count = [sum(int(num[i]) for num in vals) for i in range(len(vals[0]))]
+    return [1 if cnt >= (len(vals) - cnt) else 0 for cnt in bit_count]
+
+def reduce_reports(reports: list, invert: bool = False) -> int:
+    for i in range(0, len(reports[0])):
+        mcb = get_mcb(reports)[i]
+        bit = str(mcb if not invert else 1 - mcb)
+        reports = [rep for rep in reports if rep[i] == bit]
+        if len(reports) == 1:
+            break
+    return int(reports[0], 2)
+
+def part1(vals: list) -> int:
+    mcb = get_mcb(vals)
+    gamma = "".join(["1" if bit else "0" for bit in mcb])
+    epsilon = "".join(["0" if bit else "1" for bit in mcb])
+    return int(gamma, 2) * int(epsilon, 2)
+            
+def part2(vals: list) -> int:
+    ogr = reduce_reports(vals[:]) # oxygen generator rating
+    csr = reduce_reports(vals[:], invert=True) # CO2 scrubber rating
+    return ogr * csr
+
+if __name__ == "__main__":
+    vals = read_file()
+    print(f"Part 1: {part1(vals)}")
+    print(f"Part 2: {part2(vals)}")