Advent of Code 2023: Day #2

The idea behind the second day’s first challenge is that you have a handful of inputs given as:

Game 1: 3 blue, 4 red; 1 red, 2 green, 6 blue; 2 green

Where each line is an individual game and each set of colors and numbers is an individual pull of colored cubes from a bag. These are then placed back into the bag after each pull. The question is what is the sum of the ID’s of games that would be possible if the bag contained 12 red, 13 green and 14 blue cubes? Any individual pull that has more cubes of a given color than the bag contains would be impossible. To solve this I enumerated over all the lines in the input file as the ID is equal to the index + 1, and create a dictionary of the marbles and their current maximal values.

value = 0

file1 = open('p1_input.txt','r')
#file1 = open('p1_input.example','r')
Lines = file1.readlines()

#red, green, blue
num_marbles = [12,13,14]

for index, games in enumerate(Lines):
    max_marbles = {"green":0,"blue":0,"red":0}

Adding in some logic to parse each line into a list of strings with each string being its own pull attempt.

    games = games.split(":")
    games = games[1].replace(",","").strip()
    games = games.split(";")

where games with the Game 1 example given above would be:

['3 blue 4 red', ' 1 red 2 green 6 blue', ' 2 green']

Now I just split up each string into individual words and loop over all elements in the new array. I do this as I’m going to check if my iterating index is even and if so it means I’m on the index of a number with the next value being the associated color. I don’t need to worry about only looping over n-1 elements as I’m only looking at the n+1 value when n is even. Adding in a quick check to see if the current cubes of a a specific color is larger than the previous largest amount of that color and replacing it if it is gives:

   for game in games:
        tmp = game.split()
        for i in range(len(tmp)):
            if i % 2 == 0:
                if max_marbles[tmp[i+1]] < int(tmp[i]):
                    max_marbles[tmp[i+1]] = int(tmp[i])

Doing a simple comparison against the 12 red, 13 green, and 14 blue cubes give us if the game would be possible and an answer of 2795

if(max_marbles["red"] <= num_marbles[0] and max_marbles["green"] <= num_marbles[1] and max_marbles["blue"] <= num_marbles[2]):
    value += index+1

Here is the complete python script:

value = 0

file1 = open('p1_input.txt','r')
#file1 = open('p1_input.example','r')
Lines = file1.readlines()

#red, green, blue
num_marbles = [12,13,14]

for index, games in enumerate(Lines):
    max_marbles = {"green":0,"blue":0,"red":0}
    games = games.split(":")
    games = games[1].replace(",","").strip()
    games = games.split(";")
    for game in games:
        tmp = game.split()
        for i in range(len(tmp)):
            if i % 2 == 0:
                if max_marbles[tmp[i+1]] < int(tmp[i]):
                    max_marbles[tmp[i+1]] = int(tmp[i])
    if(max_marbles["red"] <= num_marbles[0] and max_marbles["green"] <= num_marbles[1] and max_marbles["blue"] <= num_marbles[2]):
        value += index+1

print(value)

Part 2:

Part two asks you to find what are the fewest number of each color of cube you could have to allow each individual game to be possible and take the sum of the product of each color. Using the example from part 1,

Game 1: 3 blue, 4 red; 1 red, 2 green, 6 blue; 2 green,

we would have that the minimal number of cubes needed are 4 red, 2 green, and 6 blue cubes. The product of these values (4*2*6) is 48. Conveniently, the code I used for part one only required a minor tweaking to solve part 2. I just needed to replace the check to see if the games maximum marbles are less than the allowable amount with adding the product of all the maximal marble values to my solution.

values += (max_marbles["green"] * max_marbles["red"] * max_marbles["blue"])

This gives an answer of 75561 for this days input. I have all the code used and my inputs available on my github as well as the full code for part 2 down below.

values = 0

file1 = open('p1_input.txt','r')
#file1 = open('p1_input.example','r')
Lines = file1.readlines()

#red, green, blue

for index, games in enumerate(Lines):
    max_marbles = {"green":0,"blue":0,"red":0}
    games = games.split(":")
    games = games[1].replace(",","").strip()
    games = games.split(";")
    for game in games:
        tmp = game.split()
        for i in range(len(tmp)-1):
            if i % 2 == 0:
                if max_marbles[tmp[i+1]] < int(tmp[i]):
                    max_marbles[tmp[i+1]] = int(tmp[i])
    values += (max_marbles["green"] * max_marbles["red"] * max_marbles["blue"])

print(values)