1+ import java .util .Arrays ;
2+ import java .util .HashMap ;
3+ import java .util .List ;
4+ import java .util .Map ;
5+
6+ import com .github .pareronia .aoc .solution .Sample ;
7+ import com .github .pareronia .aoc .solution .Samples ;
8+ import com .github .pareronia .aoc .solution .SolutionBase ;
9+
10+ public final class AoC2024_11 extends SolutionBase <List <Long >, Long , Long > {
11+
12+ private AoC2024_11 (final boolean debug ) {
13+ super (debug );
14+ }
15+
16+ public static AoC2024_11 create () {
17+ return new AoC2024_11 (false );
18+ }
19+
20+ public static AoC2024_11 createDebug () {
21+ return new AoC2024_11 (true );
22+ }
23+
24+ @ Override
25+ protected List <Long > parseInput (final List <String > inputs ) {
26+ return Arrays .stream (inputs .get (0 ).split (" " ))
27+ .map (Long ::valueOf )
28+ .toList ();
29+ }
30+
31+ private long solve (final List <Long > stones , final int blinks ) {
32+ class Counter {
33+ record State (long stone , int cnt ) {}
34+
35+ static final Map <State , Long > memo = new HashMap <>();
36+
37+ static long count (final long s , final int cnt ) {
38+ final State state = new State (s , cnt );
39+ if (memo .containsKey (state )) {
40+ return memo .get (state );
41+ }
42+ long ans ;
43+ if (cnt == 0 ) {
44+ ans = 1 ;
45+ } else if (s == 0 ) {
46+ ans = count (1 , cnt - 1 );
47+ } else if (String .valueOf (s ).length () % 2 == 0 ) {
48+ final String ss = String .valueOf (s );
49+ final int length = ss .length ();
50+ final long ss1 = Long .parseLong (ss .substring (0 , length / 2 ));
51+ final long ss2 = Long .parseLong (ss .substring (length / 2 ));
52+ ans = count (ss1 , cnt - 1 ) + count (ss2 , cnt - 1 );
53+ } else {
54+ ans = count (s * 2024 , cnt - 1 );
55+ }
56+ memo .put (state , ans );
57+ return ans ;
58+ }
59+ }
60+
61+ return stones .stream ().mapToLong (s -> Counter .count (s , blinks )).sum ();
62+ }
63+
64+ @ Override
65+ public Long solvePart1 (final List <Long > stones ) {
66+ return solve (stones , 25 );
67+ }
68+
69+ @ Override
70+ public Long solvePart2 (final List <Long > stones ) {
71+ return solve (stones , 75 );
72+ }
73+
74+ @ Override
75+ @ Samples ({
76+ @ Sample (method = "part1" , input = TEST , expected = "55312" )
77+ })
78+ public void samples () {
79+ }
80+
81+ public static void main (final String [] args ) throws Exception {
82+ AoC2024_11 .create ().run ();
83+ }
84+
85+ private static final String TEST = """
86+ 125 17
87+ """ ;
88+ }
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