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Commit 77cb70e

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day 22
1 parent 250acdf commit 77cb70e

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6 files changed

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6 files changed

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package com.codefork.aoc2024.day22;
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import com.codefork.aoc2024.util.Assert;
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import java.util.ArrayList;
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import java.util.HashMap;
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import java.util.LinkedList;
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import java.util.List;
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import java.util.Map;
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import java.util.stream.Collectors;
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import java.util.stream.LongStream;
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import java.util.stream.Stream;
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public class MonkeyExchangeMarket {
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public static long mix(long a, long b) {
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return a ^ b;
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}
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public static long prune(long a) {
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return a % 16777216;
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}
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public static long getNextNumber(long n) {
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var r1 = prune(mix(n * 64, n));
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var r2 = prune(mix(r1 / 32, r1));
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var r3 = prune(mix(r2 * 2048, r2));
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return r3;
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}
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public static long sum(Stream<String> data, int generations) {
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return data.mapToLong(line -> {
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var initial = Long.parseLong(line);
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return LongStream
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.range(0, generations)
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.reduce(initial, (acc, i) -> getNextNumber(acc));
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}).sum();
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}
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public static int getOnesDigit(long n) {
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var nStr = String.valueOf(n);
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var onesDigitStr = nStr.substring(nStr.length() - 1);
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return Integer.parseInt(onesDigitStr);
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}
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/*
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* generate pseudorandom numbers starting from initial, for max iterations,
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* and return a map of 4-change sequences to the price at that sequence.
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*/
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public static Map<List<Integer>, Integer> createChangesMap(long initial, int max) {
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var number = initial;
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var i = 0;
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var lastChanges = new LinkedList<Integer>();
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var changesToPrice = new HashMap<List<Integer>, Integer>();
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while(i < max) {
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var numberOnesDigit = getOnesDigit(number);
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var newNumber = getNextNumber(number);
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var newNumberOnesDigit = getOnesDigit(newNumber);
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var change = newNumberOnesDigit - numberOnesDigit;
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lastChanges.add(change);
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if (lastChanges.size() == 5) {
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lastChanges.removeFirst();
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}
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if (lastChanges.size() == 4) {
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var changesKey = new ArrayList<>(lastChanges);
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// only store it if this is the first time we've seen it
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if (!changesToPrice.containsKey(changesKey)) {
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//System.out.println("adding key=" + changesKey + " value=" + newNumberOnesDigit);
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changesToPrice.put(changesKey, newNumberOnesDigit);
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} else {
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//System.out.println("already seen key=" + changesKey);
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}
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}
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// if (i == 0) {
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// System.out.println(number + ": " + numberOnesDigit);
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// }
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// System.out.println(newNumber + ": " + newNumberOnesDigit + " (" + change + ")");
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// update all our state variables
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number = newNumber;
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i++;
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}
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return changesToPrice;
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}
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public record Sequence(List<Integer> seq, int totalBananas) {
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}
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public static Sequence findSequence(Stream<String> data, int generations) {
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record Flat(List<Integer> changes, Integer price) {
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}
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var results = data
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.map(line -> createChangesMap(Long.parseLong(line), generations))
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.flatMap(changesMap ->
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// transform key/value pairs in map to a list
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changesMap.entrySet().stream().map(entry ->
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new Flat(entry.getKey(), entry.getValue())
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)
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)
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.toList();
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// group the Flats by changes
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var byChanges = results.stream()
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.collect(Collectors.groupingBy(Flat::changes));
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// sum the Flats in the values part of map
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var changesToSums = byChanges.entrySet().stream()
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.collect(Collectors.toMap(
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Map.Entry::getKey,
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(entry) ->
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entry.getValue().stream().mapToInt(Flat::price).sum()
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)
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);
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var highestTotal = changesToSums.values().stream().mapToInt(i -> i).max().orElseThrow();
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var changesFound = changesToSums.keySet().stream()
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.filter(changes -> Integer.valueOf(highestTotal).equals(changesToSums.get(changes)))
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.toList();
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Assert.assertEquals(1, changesFound.size());
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return new Sequence(changesFound.getFirst(), highestTotal);
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}
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}
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package com.codefork.aoc2024.day22;
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import com.codefork.aoc2024.Problem;
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import com.codefork.aoc2024.util.Assert;
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import java.util.stream.Stream;
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public class Part01 extends Problem {
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public String solve(Stream<String> data) {
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var result = MonkeyExchangeMarket.sum(data, 2000);
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return String.valueOf(result);
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}
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@Override
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public String solve() {
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Assert.assertEquals("37327623", solve(getSampleInput()));
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return solve(getInput());
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}
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public static void main(String[] args) {
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new Part01().run();
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}
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}
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package com.codefork.aoc2024.day22;
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import com.codefork.aoc2024.Problem;
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import com.codefork.aoc2024.util.Assert;
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import java.util.List;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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public class Part02 extends Problem {
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public String seqToString(List<Integer> seq) {
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return seq.stream().map(String::valueOf).collect(Collectors.joining(","));
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}
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public MonkeyExchangeMarket.Sequence solve(Stream<String> data) {
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return MonkeyExchangeMarket.findSequence(data, 2000);
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}
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@Override
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public String solve() {
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var sampleSeq = solve(getFileAsStream("sample2"));
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Assert.assertEquals("-2,1,-1,3", seqToString(sampleSeq.seq()));
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Assert.assertEquals(23, sampleSeq.totalBananas());
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return String.valueOf(solve(getInput()).totalBananas());
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}
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public static void main(String[] args) {
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new Part02().run();
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}
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}
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‎src/main/resources/day22/input

12.3 KB
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‎src/main/resources/day22/sample

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‎src/main/resources/day22/sample2

33 Bytes
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