5

solutions/5/README.md

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+# 5
+
+For the first one we treat the codes as 2 binary codes. One 7 and the other 3 long.
+
+The second tripped me up as I was returning the binary encoded ticket number but AOC was expecting the seat ID. My bad, took me long to get it. Thanks to @tcq1
+
+<details>
+  <summary>Solutions</summary>
+  <ol>
+    <li>998</li>
+    <li>84, 4 -> 676</li>
+  </ol>
+</details>

solutions/5/python/main.py

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+from os.path import join, dirname
+from itertools import product
+from typing import Tuple
+
+
+def from_binary(code: str, high: str) -> int:
+    return int(''.join([
+        '1' if char == high else '0'
+        for char in code
+    ]), 2)
+
+
+def read_seat(seat) -> Tuple[int, int]:
+    row_raw = seat[:-3]
+    column_raw = seat[-3:]
+    row = from_binary(row_raw, 'B')
+    column = from_binary(column_raw, 'R')
+    return row, column
+
+
+def seat_code(row: int, column: int) -> int:
+    return row * 8 + column
+
+
+data = join(dirname(__file__), '../data.txt')
+with open(data) as f:
+    seats = f.read().strip().split('\n')
+
+    free = list(product(range(4, 126), range(8)))
+    maximum = 0
+    for seat in seats:
+        row, column = read_seat(seat)
+        m = row * 8 + column
+        maximum = max(maximum, m)
+        free.remove((row, column))
+
+    print(f"Highers ID:\t{maximum}")
+
+    # Find the remaining seat
+    row_max = 0
+    row_min = 128
+    for row, _ in free:
+        row_max = max(row_max, row)
+        row_min = min(row_min, row)
+    remaining = [
+        (row, column)
+        for row, column in free
+        if row >= row_min + 1 and row <= row_max - 2
+    ][0]
+    my_ticket = seat_code(*remaining)
+    print(f"My Ticket:\t{my_ticket}")