11package com .sbaars .adventofcode .year17 .days ;
22
33import com .sbaars .adventofcode .year17 .Day2017 ;
4- import java .util .Arrays ;
5- import java .util .HashSet ;
6- import java .util .Set ;
4+ import java .util .*;
75
86public class Day6 extends Day2017 {
97
@@ -15,69 +13,66 @@ public static void main(String[] args) {
1513 new Day6 ().printParts ();
1614 }
1715
16+ private String getState (int [] banks ) {
17+ StringBuilder sb = new StringBuilder ();
18+ for (int bank : banks ) {
19+ sb .append (bank ).append (',' );
20+ }
21+ return sb .toString ();
22+ }
23+ 24+ private int [] redistribute (int [] banks ) {
25+ int [] newBanks = banks .clone ();
26+ int maxIndex = 0 ;
27+ int maxValue = newBanks [0 ];
28+ 29+ // Find bank with most blocks
30+ for (int i = 1 ; i < newBanks .length ; i ++) {
31+ if (newBanks [i ] > maxValue ) {
32+ maxValue = newBanks [i ];
33+ maxIndex = i ;
34+ }
35+ }
36+ 37+ // Redistribute blocks
38+ newBanks [maxIndex ] = 0 ;
39+ int index = (maxIndex + 1 ) % newBanks .length ;
40+ while (maxValue > 0 ) {
41+ newBanks [index ]++;
42+ maxValue --;
43+ index = (index + 1 ) % newBanks .length ;
44+ }
45+ 46+ return newBanks ;
47+ }
48+ 1849 @ Override
1950 public Object part1 () {
2051 int [] banks = Arrays .stream (day ().trim ().split ("\t " )).mapToInt (Integer ::parseInt ).toArray ();
2152 Set <String > seen = new HashSet <>();
2253 int cycles = 0 ;
2354
24- while (true ) {
25- String state = Arrays .toString (banks );
26- if (!seen .add (state )) {
27- return cycles ;
28- }
29- 30- // Find bank with most blocks
31- int maxIndex = 0 ;
32- for (int i = 1 ; i < banks .length ; i ++) {
33- if (banks [i ] > banks [maxIndex ]) {
34- maxIndex = i ;
35- }
36- }
37- 38- // Redistribute blocks
39- int blocks = banks [maxIndex ];
40- banks [maxIndex ] = 0 ;
41- for (int i = 0 ; i < blocks ; i ++) {
42- banks [(maxIndex + 1 + i ) % banks .length ]++;
43- }
44- 55+ while (seen .add (getState (banks ))) {
56+ banks = redistribute (banks );
4557 cycles ++;
4658 }
59+ 60+ return cycles ;
4761 }
4862
4963 @ Override
5064 public Object part2 () {
5165 int [] banks = Arrays .stream (day ().trim ().split ("\t " )).mapToInt (Integer ::parseInt ).toArray ();
52- Set <String > seen = new HashSet <>();
66+ Map <String , Integer > seen = new HashMap <>();
5367 int cycles = 0 ;
54- String firstRepeat = null ;
5568
5669 while (true ) {
57- String state = Arrays .toString (banks );
58- if (state .equals (firstRepeat )) {
59- return cycles ;
60- }
61- if (!seen .add (state )) {
62- firstRepeat = state ;
63- cycles = 0 ;
64- }
65- 66- // Find bank with most blocks
67- int maxIndex = 0 ;
68- for (int i = 1 ; i < banks .length ; i ++) {
69- if (banks [i ] > banks [maxIndex ]) {
70- maxIndex = i ;
71- }
72- }
73- 74- // Redistribute blocks
75- int blocks = banks [maxIndex ];
76- banks [maxIndex ] = 0 ;
77- for (int i = 0 ; i < blocks ; i ++) {
78- banks [(maxIndex + 1 + i ) % banks .length ]++;
70+ String state = getState (banks );
71+ if (seen .containsKey (state )) {
72+ return cycles - seen .get (state );
7973 }
80- 74+ seen .put (state , cycles );
75+ banks = redistribute (banks );
8176 cycles ++;
8277 }
8378 }
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