1+ package com .macasaet ;
2+
3+ import org .junit .jupiter .api .Test ;
4+
5+ import java .util .ArrayList ;
6+ import java .util .Collections ;
7+ import java .util .HashSet ;
8+ import java .util .List ;
9+ import java .util .Set ;
10+ import java .util .stream .Stream ;
11+ import java .util .stream .StreamSupport ;
12+
13+ /**
14+ * --- Day 3: Rucksack Reörganisation ---
15+ * https://adventofcode.com/2022/day/3
16+ */
17+ public class Day03 {
18+
19+ protected static int priority (final char c ) {
20+ if (c >= 'a' && c <= 'z' ) {
21+ return c - 'a' + 1 ;
22+ }
23+ return c - 'A' + 27 ;
24+ }
25+
26+ protected Stream <Rucksack > getInput () {
27+ return StreamSupport
28+ .stream (new LineSpliterator ("day-03.txt" ),
29+ false )
30+ .map (Rucksack ::parse );
31+ }
32+
33+ @ Test
34+ public final void part1 () {
35+ final var result = getInput ().mapToInt (Rucksack ::priority ).sum ();
36+
37+ System .out .println ("Part 1: " + result );
38+ }
39+
40+ @ Test
41+ public final void part2 () {
42+ final var groups = new ArrayList <List <Rucksack >>();
43+ var currentGroup = new ArrayList <Rucksack >(3 );
44+
45+ for (final var i = getInput ().iterator (); i .hasNext (); ) {
46+ final var rucksack = i .next ();
47+ if (currentGroup .size () == 3 ) {
48+ groups .add (Collections .unmodifiableList (currentGroup ));
49+ currentGroup = new ArrayList <>(3 );
50+ }
51+ currentGroup .add (rucksack );
52+ }
53+ if (currentGroup .size () == 3 ) {
54+ groups .add (Collections .unmodifiableList (currentGroup ));
55+ }
56+ final var result = groups .stream ().map (this ::getBadge ).mapToInt (Day03 ::priority ).sum ();
57+
58+ System .out .println ("Part 2: " + result );
59+ }
60+
61+ protected char getBadge (final List <? extends Rucksack > group ) {
62+ final var first = group .get (0 );
63+ for (final var item : first .allItems ()) {
64+ if (group .get (1 ).allItems ().contains (item ) && group .get (2 ).allItems ().contains (item )) {
65+ return item ;
66+ }
67+ }
68+ throw new IllegalStateException ();
69+ }
70+
71+ /**
72+ * An Elf's container of supplies for a jungle journey. "Each rucksack has two large compartments. All items of a
73+ * given type are meant to go into exactly one of the two compartments."
74+ *
75+ * @param firstCompartment All the items in one compartment
76+ * @param secondCompartment All the items in one compartment
77+ * @param allItems All the items
78+ */
79+ public record Rucksack (Set <Character > firstCompartment , Set <Character > secondCompartment , Set <Character > allItems ) {
80+
81+ public static Rucksack parse (final String line ) {
82+ final var chars = line .toCharArray ();
83+ if (chars .length % 2 != 0 ) {
84+ throw new IllegalArgumentException ();
85+ }
86+ final var firstCompartment = new HashSet <Character >(chars .length / 2 );
87+ final var secondCompartment = new HashSet <Character >(chars .length / 2 );
88+ for (int i = 0 ; i < chars .length / 2 ; i ++) {
89+ firstCompartment .add (chars [i ]);
90+ }
91+ for (int i = chars .length / 2 ; i < chars .length ; i ++) {
92+ secondCompartment .add (chars [i ]);
93+ }
94+ final var union = new HashSet <Character >(chars .length );
95+ union .addAll (firstCompartment );
96+ union .addAll (secondCompartment );
97+ return new Rucksack (Collections .unmodifiableSet (firstCompartment ),
98+ Collections .unmodifiableSet (secondCompartment ),
99+ Collections .unmodifiableSet (union ));
100+ }
101+
102+ public int priority () {
103+ final var intersection = new HashSet <Character >();
104+ for (final char c : firstCompartment ) {
105+ if (secondCompartment .contains (c )) {
106+ intersection .add (c );
107+ }
108+ }
109+ if (intersection .size () != 1 ) {
110+ throw new IllegalStateException ("There should only be one common item between compartments" );
111+ }
112+ return Day03 .priority (intersection .iterator ().next ());
113+ }
114+
115+
116+ }
117+ }
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