Advent of Code 2022 - Day 1

Useful Links

Concepts and Packages Demonstrated

Problem Intro
Part 1
Part 2
Results

Problem Intro

As usual AoC starts with an easy challenge. This one took me about a minute to write. But if you’re new to AoC, or to Python, don’t sweat it! My first ever Day 1 - when I was learning Python - took me about 30 minutes!

Check out my Python Journey pages to read more about the concepts and modules I use in these solutions.

For this challenge, we’re told that the elves are on an expedition. Each elf is carrying a number of meals, and each meal contains a specific number of calories. This is our input data. Specifically:

Our input data contains lines of numbers, with occasional empty lines.
Each line is a number, representing the calories for an elf meal.
Each contiguous block of lines represents the meals for a given elf.
The empty lines separate one elf from the next.

So the input data looks something like this:

Part 1

Find the Elf carrying the most Calories. How many total Calories is that Elf carrying?

Okay, so what we need to do is find the block of numbers that adds up to the largest value.

Here’s how I did it:

Read the data, and split by empty lines, to return a list.
Each element in the list is a single str, containing all the meal calorie values for that elf. Each calorie value is separated by a single newline character. (Because all the calorie values were on separate lines.)
Split this str into its constituent numbers, by using splitlines(). Each calorie value is returned as a str.
Convert every number str to an int. The Pythonic way to do this is using the map() function.
Sum these numbers. This gives us the total calorie count for each elf. Add this count to a list.
Finally, use max() to return the biggest number in our list.

Here is the code:

from pathlib import Path
import time

SCRIPT_DIR = Path(__file__).parent
# INPUT_FILE = Path(SCRIPT_DIR, "input/sample_input.txt")
INPUT_FILE = Path(SCRIPT_DIR, "input/input.txt")

def main():
    with open(INPUT_FILE, mode="rt") as f:
        elf_meals = f.read().split("\n\n") # split on empty lines
    
    elf_calories = [] # store total calories for each elf
    for elf in elf_meals:
        calories = sum(map(int, elf.splitlines()))
        elf_calories.append(calories)
        
    print(f"Part 1: {max(elf_calories)}")

if __name__ == "__main__":
    t1 = time.perf_counter()
    main()
    t2 = time.perf_counter()
    print(f"Execution time: {t2 - t1:0.4f} seconds")

Part 2

Find the top three Elves carrying the most Calories. How many Calories are those Elves carrying in total?

This is easy to do. My solution:

Take the list of calories that we obtained before, and sort it in ascending numerical order.
Then use a slice to return the last three values. Here our slice is [-3:]. That means, get all the elements starting with the third from the end (because -1 is the last, -2 is adjacent to the last, and so on), all the way to the last element (inclusive).
Then sum the slice.

So, we just need to add this to our main() method:

    elf_calories = sorted(elf_calories)
    print(f"Part 2: {sum(elf_calories[-3:])}")

Results

The output looks like this:

Part 1: 67016
Part 2: 200116
Execution time: 0.0007 seconds

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