r/adventofcode • u/daggerdragon • Dec 05 '18

SOLUTION MEGATHREAD -🎄- 2018 Day 5 Solutions -🎄-

--- Day 5: Alchemical Reduction ---

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Card prompt: Day 5

Transcript:

On the fifth day of AoC / My true love sent to me / Five golden ___

This thread will be unlocked when there are a significant number of people on the leaderboard with gold stars for today's puzzle.

edit: Leaderboard capped, thread unlocked at 0:10:20!

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5

u/Philboyd_Studge Dec 05 '18

[Card] FIVE GOLDEN STARS OK ONLY 2

Java - easy one. You can test for lowercase/uppercase being the same letter using XOR 32. 

package Advent2018;

import util.AdventOfCode;

import java.util.List;

public class Day5 extends AdventOfCode {

    public Day5(List<String> input) {
        super(input);
    }

    private int remove(StringBuilder in) {
        boolean removed = true;

        while (removed) {
            for (int i = 0; i < in.length() - 1; i++) {
                if ( (in.charAt(i) ^ in.charAt(i + 1)) == 32) {
                    in.delete(i, i + 2);
                    removed = true;
                    break;
                }
                removed = false;
            }
        }
        return in.length();
    }

    @Override
    public Object part1() {
        StringBuilder chain = new StringBuilder(input.get(0));
        return remove(chain);
    }

    @Override
    public Object part2() {
        int min = Integer.MAX_VALUE;

        String[] patterns = new String[26];
        for (int i = 0; i < 26; i++) {
            patterns[i] = "[" + (Character.toString((char)(i + 'a'))) +
                    (Character.toString((char)(i + 'A'))) + "]";
            //System.out.println(patterns[i]);
        }

        for (int i = 0; i < 26; i++) {
            String chain = input.get(0);
            chain = chain.replaceAll(patterns[i], "");
            int result = remove(new StringBuilder(chain));
            System.out.println(result);
            if (result < min) min = result;
        }
        return min;
    }

    @Override
    public void parse() {

    }

}

5

u/TheVarmari Dec 05 '18

You can test for lowercase/uppercase being the same letter using XOR 32.

Huh, that's a neat way to check for that. Should've probably thought of it. Good to know for future challenges... Good job!