Advent of Code 2021 Python Solution: Day 6

Today's challenge was easy but tricky one. I found 4th day's challenge to be more tough than today's but still I had hard time finding the right way to loop through all days.

Part 1

data,data1 = get_data(day=6)
data = [int(d) for d in data[0].split(",")]
data1 = [int(d) for d in data1[0].split(",")]

days = {}
total_days = 81
curr_data = data1.copy()
for day in range(1, total_days):    
    temp_data = []
    new_fish = []
    for d in curr_data:
        if d == 0:
            new_fish.append(8)
            d=6
        else:
            d-=1
        temp_data.append(d)
    temp_data.extend(new_fish)
    curr_data = temp_data
print(f"Total Fish: {len(curr_data)}\n")

Answer was:

Total Fish: 388419

It took around 2 seconds to run above code while total_days was 81 but when total_day was 257, it seemed like loop will be going on forever. And total fish keeps increasing by time. I even tried to make things faster by using NumPy but it did not work out. Thus, I used dictionaries to store lifespans of fish. Since it could be one of the 0 to 8, why bother keeping lifes?

Part 2

from collections import Counter

lifes = dict(Counter(data1))

days = 256
for day in range(1, days+1):
    lifes = {l: (0 if lifes.get(l+1) is None else lifes.get(l+1)) for l in range(-1, 8)}
    # make all 8s -1 because we create new fish with 8 after it reaches 0
    lifes[8] = lifes[-1]
    # add new lifes to that are exhausted
    lifes[6] += lifes[-1]
    # reset exhausted lifes
    lifes[-1] = 0 

print(sum(lifes.values()))

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Advent of Code 2021 Python Solution: Day 6

Viper

Part 1

Part 2

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