Day 6 was another text parsing challenge, breaking the input into groups and then counting across the users within each group. Both parts were similar, with the first counting if any user said yes to a given question, and the latter if every user said yes to a given question. Python makes this a breeze either way.

## Challenge

The puzzle can be found here. I’m given text again representing answers to 26 questions from people. Each person’s answers are on one line, and each group of people is seperated by an empty line. In part one, I’m asked to look at each group and count the number of questions that were included by any one member, and sum that count across all groups. In part two, I’m asked to count a question only if every member said yes.

## Solution

### Part 1

This is another one where Python makes it too easy. Once I break the text into groups (using split('\n\n')), I just need to remove the newlines and then get the set (list of unique items) of characters that remain. The length of that set is the count for the group. So loop over all groups getting that length, and then sum it to get the total:

#!/usr/bin/env python3

import sys

with open(sys.argv[1], "r") as f:

part1 = sum([len(set(ans.replace("\n", ""))) for ans in answers])
print(f"Part 1: {part1}")


### Part 2

For part two, I need to look at each member of the group to ensure they included the answer before counting it. I’ll loop through the characters a-z, and check that that character is in all the members for the group, and if so, count it. I’ll just use one count across all groups, as I don’t need to track the per group total:

#!/usr/bin/env python3

import string
import sys

with open(sys.argv[1], "r") as f:

part1 = sum([len(set(ans.replace("\n", ""))) for ans in answers])
print(f"Part 1: {part1}")

count = 0
ind_ans = ans.split("\n")
for c in string.ascii_lowercase:
count += all([c in a for a in ind_ans])

print(f"Part 2: {count}")


These both solve instantly:

\$ time python3 day6.py 06-puzzle_input.txt
Part 1: 6534
Part 2: 3402

real    0m0.061s
user    0m0.049s
sys     0m0.012s