AOC 2018 - Day 2 - Python

aoc2018_day2.py

# Part 1

from collections import Counter
lines = [line.strip() for line in open('day2.txt')]
twos = 0
threes = 0
for line in lines:
    counts = {l: c for l, c in Counter([l for l in line]).items()}
    twos += 1 if 2 in counts.values() else 0
    threes += 1 if 3 in counts.values() else 0
print(str(twos * threes))

# Part 1 - Alternative (no imports)

lines = [line.strip() for line in open('day2.txt')]
twos = 0
threes = 0
for line in lines:
    letters = {}
    for letter in line:
        letters[letter] = letters[letter] + 1 if letter in letters else 1
    twosCounted = False
    threesCounted = False
    for letter in letters:
        if letters[letter] == 2 and not twosCounted:
            twos += 1
            twosCounted = True
        elif letters[letter] == 3 and not threesCounted:
            threes += 1
            threesCounted = True
print(str(twos * threes))

# Part 2

lines = [line.strip() for line in open('day2.txt')]
found = False # just for a bit of optimization when answer has been found
for i in range(0, len(lines)):
    if found:
        break
    a = lines[i]
    for j in range(i + 1, len(lines)):
        b = lines[j]
        diff = 0
        k = 0
        letters = ""
        while diff <= 1 and k < len(a):
            if a[k] != b[k]:
                diff += 1
            else:
                letters += a[k]
            k += 1
        if diff == 1:
            print(letters)
            found = True
            break