AOC 2018 - Day 5 - Python

aoc2018_day5.py

# Input

polymer = [unit for  unit in ''.join([line.strip() for line in open('day5.txt')])]

# Part 1 (+ function also used for part 2)

def react(polymer):
    i = 0
    while i + 1 < len(polymer):
        unit1 = polymer[i]
        unit2 = polymer[i + 1]
        if unit1 != unit2 and unit1.lower() == unit2.lower():
            del polymer[i]
            del polymer[i]
            i -= 1
        else:
            i += 1
    return len(polymer)
print(react(polymer))

# Part 2

units = set([unit.lower() for unit in polymer])
minLength = len(polymer)
for unit in units:
    newPolymer = list(filter(lambda u: u.lower() != unit, polymer))
    minLength = min(minLength, react(newPolymer))
print(minLength)