Sean McLemon | Advent of Code

2022-12-02 - Rock Paper Scissors

(original .ipynb)

Day 2 puzzle input is a sequence of either A, B or C followed by either X, Y or Z (mine is here). Part 1 involves interpreting these as a set of instructions as to what you and an opponent will play in rock, paper scissors and calculating a score. Part 2 involves interpreting these slightly differently (what your opponent will play, and whether you should win, lose or draw) then calculating the score as before.

puzzle_input_str = open("./puzzle_input/day2.txt").read()

test_input_str = """A Y
B X
C Z"""

rock, paper, scissors = ("A", "B", "C")
shape_score = {rock: 1,        paper: 2,        scissors: 3}
defeats     = {rock: paper,    paper: scissors, scissors: rock}
defeated_by = {rock: scissors, paper: rock,     scissors: paper}


def guessed_parser(line):
    # guess that X/Y/Z maps to rock/paper/scissors
    first, second = line.split(" ")
    return first, chr(ord(second) + ord(rock) - ord("X"))


def part_one(input_str, parse_line=guessed_parser):
    my_score = 0
    for line in input_str.split("\n"):
        theirs, mine = parse_line(line)
        my_score += shape_score[mine]
        
        if theirs == mine:
            my_score += 3
        elif defeated_by[mine] == theirs:
            my_score += 6
            
    return my_score


assert 15 == part_one(test_input_str)

print("part one:", part_one(puzzle_input_str))

part one: 11150

def outcome_parser(line):
    theirs, outcome = line.split(" ")
    if outcome == "X":   # lose
        return (theirs, defeated_by[theirs])
    elif outcome == "Y": # draw
        return (theirs, theirs)
    else:                # win
        return (theirs, defeats[theirs])


def part_two(input_str):
    return part_one(input_str, outcome_parser)


assert 12 == part_two(test_input_str)

print("part two:", part_two(puzzle_input_str))

part two: 8295