import 2020 aoc

2020/day5/day5.py

@@ -0,0 +1,69 @@
+#! /usr/bin/env python3
+from itertools import product
+from bisect import bisect
+
+
+def main(filename):
+    results = {}
+    with open(filename) as inp:
+        for line in inp:
+            boarding_pass = line.rstrip()
+            row, col = parse_boarding_pass(boarding_pass)
+            seat_id = get_seat_id(row, col)
+            results[boarding_pass] = (row, col, seat_id)
+    part1(results)
+    part2(results)
+
+
+def part1(results):
+    # part 1
+    max_seat_id = max(x[2] for x in results.values())
+    print("Max seat ID: ", max_seat_id)
+
+
+def part2(results):
+    seat_ids = sorted(x[2] for x in results.values())
+    missing_seat_ids = set(range(max(seat_ids))) - set(seat_ids)
+    print("Your seat id : ", max(missing_seat_ids))
+
+
+def parse_boarding_pass(boarding_pass, strategy="binary"):
+    "Poor man's dispatcher"
+    try: 
+        to_call = globals()[f"parse_boarding_pass_{strategy}"]
+        return to_call(boarding_pass)
+    except KeyError:
+        raise KeyError(f"Bad strategy name {strategy}")
+
+
+def parse_boarding_pass_binary(boarding_pass):
+    "Parse boarding pass using a binary conversion"
+    boarding_pass = boarding_pass.translate(str.maketrans("FLBR", "0011"))
+    row = boarding_pass[:7]
+    col = boarding_pass[7:]
+    return int(row, base=2), int(col, base=2)
+
+
+def parse_boarding_pass_bisect(boarding_pass):
+    "Pass boarding pass using bisection algorithm"
+    row = bisect(boarding_pass[:7], lower_option="F", upper_option="B", max=127)
+    col = bisect(boarding_pass[7:], lower_option="L", upper_option="R", max=7)
+    return row, col
+
+
+def bisect(inp, lower_option, upper_option, max):
+    min_v, max_v = 0, max
+    for l in inp:
+        length = max_v - min_v
+        if l == lower_option:
+            max_v = min_v + length // 2
+        elif l == upper_option:
+            min_v = 1 + min_v + length // 2
+    return min_v
+
+def get_seat_id(row, col):
+    return 8 * row + col
+
+
+if __name__ == "__main__":
+    main('input.txt')