Discussion on: Advent of Code 2020 Solution Megathread - Day 5: Binary Boarding

[Anvesh Saxena]

Part 2 of the puzzle was really puzzling, though I got the answer using set theory

import sys
import math #for ceil and floor functions

def row_search(seat):
    upper = 127
    lower = 0
    for character in seat[0:7]:
        if character == "F":
            upper = math.floor((lower + upper)/2)
        elif character == "B":
            lower = math.ceil((lower+upper)/2)
        #print("Character {} Lower {} Upper {}".format(character, lower, upper))
    return upper

def column_search(seat):
    right = 7
    left = 0
    #print(seat[-3:])
    for character in seat[-3:]:
        if character == "R":
            left = math.ceil((right+left)/2)
        elif character == "L":
            right = math.floor((right+left)/2)
        #print("Character {} left {} right {}".format(character, left, right))
    return right

highest = 0
seat_list = []
full_seats = range(0,1023)
for boarding_pass in sys.stdin:
        #print(row_search(boarding_pass.rstrip("\n")))
        #print(column_search(boarding_pass.rstrip("\n")))
        #print(row_search(boarding_pass.rstrip("\n")) * 8 + column_search(boarding_pass.rstrip("\n")))
        seat_list.append(row_search(boarding_pass.rstrip("\n")) * 8 + column_search(boarding_pass.rstrip("\n")))
        if highest < row_search(boarding_pass.rstrip("\n")) * 8 + column_search(boarding_pass.rstrip("\n")):
            highest = row_search(boarding_pass.rstrip("\n")) * 8 + column_search(boarding_pass.rstrip("\n"))

print(highest)
print(len(seat_list))
print(set(full_seats) - set(seat_list))