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Advent of Code 2021 Python Solution: Day 6

#adventofcode #python #algorithms

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")
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Answer was:

Total Fish: 388419
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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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