2020-12-15 - Rambunctious Recitation
(original .ipynb)
Day 15 puzzle input is a comma-separated sequence of integers (mine is here) which represent the first few numbers spoken as part of an elf memory game. Part 1 involves playing the game until turn 2020 - and the last number spoken is the answer. Part 2 involves running the game for 30 million turns, and the last number spoken is the answer.
test_input_str = """0,3,6"""
puzzle_input_str = open("puzzle_input/day15.txt", "r").read()
def solve(input_str, n=2020):
input_lst = [int(s) for s in input_str.split(",")]
last_seen = {s:i for i, s in enumerate(input_lst[:-1])}
turn = len(input_lst)
number_spoken = input_lst[-1]
#-----------------------
while turn < n:
if not (number_spoken in last_seen):
new_number_spoken = 0
else:
new_number_spoken = turn - 1 - last_seen[number_spoken]
last_seen[number_spoken] = turn - 1
number_spoken = new_number_spoken
turn += 1
#-----------------------
return number_spoken
assert 436 == solve(test_input_str)
# Given the starting numbers 1,3,2, the 2020th number spoken is 1.
# Given the starting numbers 2,1,3, the 2020th number spoken is 10.
# Given the starting numbers 1,2,3, the 2020th number spoken is 27.
# Given the starting numbers 2,3,1, the 2020th number spoken is 78.
# Given the starting numbers 3,2,1, the 2020th number spoken is 438.
# Given the starting numbers 3,1,2, the 2020th number spoken is 1836.
assert 1 == solve("1,3,2")
assert 10 == solve("2,1,3")
assert 27 == solve("1,2,3")
assert 78 == solve("2,3,1")
assert 438 == solve("3,2,1")
assert 1836 == solve("3,1,2")
solve(puzzle_input_str)
232
%%time
# Given 0,3,6, the 30000000th number spoken is 175594.
# Given 1,3,2, the 30000000th number spoken is 2578.
# Given 2,1,3, the 30000000th number spoken is 3544142.
# Given 1,2,3, the 30000000th number spoken is 261214.
# Given 2,3,1, the 30000000th number spoken is 6895259.
# Given 3,2,1, the 30000000th number spoken is 18.
# Given 3,1,2, the 30000000th number spoken is 362.
assert 175594 == solve("0,3,6", 30_000_000)
assert 2578 == solve("1,3,2", 30_000_000)
assert 3544142 == solve("2,1,3", 30_000_000)
assert 261214 == solve("1,2,3", 30_000_000)
assert 6895259 == solve("2,3,1", 30_000_000)
assert 18 == solve("3,2,1", 30_000_000)
assert 362 == solve("3,1,2", 30_000_000)
solve(puzzle_input_str, 30_000_000)
CPU times: user 2min 37s, sys: 2.7 s, total: 2min 40s Wall time: 2min 42s
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