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SvenWoltmannSvenWoltmann
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Add day 21 solution
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‎src/main/java/eu/happycoders/adventofcode2022/day21/Day21Solver.java‎

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package eu.happycoders.adventofcode2022.day21;
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import java.util.Map;
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/**
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* Advent of Code 2022 – Object-Oriented Solutions in Java.
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*
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* <p>Puzzle solver for day 21.
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*
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* @author <a href="mailto:sven@happycoders.eu">Sven Woltmann</a>
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*/
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class Day21Solver {
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static long solveTask1(String input) {
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Map<String, Job> jobMap = JobsParser.parse(input);
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Jobs jobs = new Jobs(jobMap);
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return jobs.solve();
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}
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static long solveTask2(String input) {
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Map<String, Job> jobMap = JobsParser.parse(input);
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Jobs jobs = new Jobs(jobMap);
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return jobs.findNumberForHumanIfRootOperandsMustBeEqual();
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}
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}

‎src/main/java/eu/happycoders/adventofcode2022/day21/Job.java‎

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package eu.happycoders.adventofcode2022.day21;
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/**
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* Advent of Code 2022 – Object-Oriented Solutions in Java.
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*
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* <p>Abstract base class for a job given to a monkey.
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*
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* @author <a href="mailto:sven@happycoders.eu">Sven Woltmann</a>
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*/
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abstract sealed class Job permits NumberJob, MathOperationJob {
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private final String monkeyName;
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Job(String monkeyName) {
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this.monkeyName = monkeyName;
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}
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String monkeyName() {
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return monkeyName;
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}
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abstract Long result();
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}

‎src/main/java/eu/happycoders/adventofcode2022/day21/Jobs.java‎

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package eu.happycoders.adventofcode2022.day21;
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import java.util.List;
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import java.util.Map;
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class Jobs {
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private static final String ROOT = "root";
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private static final String HUMAN = "humn";
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private final List<Job> allJobs;
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private final Job rootJob;
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private final Job humanJob;
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Jobs(Map<String, Job> monkeyNameToJob) {
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this.allJobs = List.copyOf(monkeyNameToJob.values());
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this.rootJob = monkeyNameToJob.get(ROOT);
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this.humanJob = monkeyNameToJob.get(HUMAN);
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}
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long solve() {
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return solve(rootJob);
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}
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private long solve(Job job) {
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return switch (job) {
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case NumberJob numberJob -> numberJob.result();
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case MathOperationJob mathOperationJob -> solveMathOperationJob(mathOperationJob);
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};
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}
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private long solveMathOperationJob(MathOperationJob mathOperationJob) {
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Long cachedResult = mathOperationJob.result();
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if (cachedResult != null) {
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return cachedResult;
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}
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long operand1 = solve(mathOperationJob.operand1Job());
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long operand2 = solve(mathOperationJob.operand2Job());
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long result = mathOperationJob.apply(operand1, operand2);
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mathOperationJob.setCachedResult(result);
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return result;
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}
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long findNumberForHumanIfRootOperandsMustBeEqual() {
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solve();
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removeCachedResultsFromRootToHuman();
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return applyReverseOperationsFromRootToHuman();
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}
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private void removeCachedResultsFromRootToHuman() {
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while (true) {
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for (Job job : allJobs) {
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if (isOperationWithResultAndOneOperandHavingNoResultOrBeingHuman(job)) {
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((MathOperationJob) job).setCachedResult(null);
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if (job == rootJob) {
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return;
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}
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}
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}
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}
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}
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private boolean isOperationWithResultAndOneOperandHavingNoResultOrBeingHuman(Job job) {
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return job.result() != null
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&& job instanceof MathOperationJob operation
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&& (getResultOrNullIfHuman(operation.operand1Job()) == null
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|| getResultOrNullIfHuman(operation.operand2Job()) == null);
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}
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private Long getResultOrNullIfHuman(Job job) {
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return job == humanJob ? null : job.result();
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}
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private long applyReverseOperationsFromRootToHuman() {
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return applyReverseOperationsDownToHuman((MathOperationJob) rootJob, 0);
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}
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private long applyReverseOperationsDownToHuman(MathOperationJob job, long lastValue) {
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Long operand1 = getResultOrNullIfHuman(job.operand1Job());
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Long operand2 = getResultOrNullIfHuman(job.operand2Job());
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// Either go down the left path...
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if (operand1 == null && operand2 != null) {
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return applyReverseOperationsDownToHumanViaOperand1(job, lastValue, operand2);
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}
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// ... or the right path
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if (operand1 != null && operand2 == null) {
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return applyReverseOperationsDownToHumanViaOperand2(job, lastValue, operand1);
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}
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throw new IllegalStateException();
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}
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private long applyReverseOperationsDownToHumanViaOperand1(
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MathOperationJob job, long lastValue, Long operand2) {
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Long operand1;
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if (job == rootJob) {
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operand1 = operand2;
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} else {
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operand1 = job.applyReverseToFindOperand1(lastValue, operand2);
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}
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if (job.operand1Job() == humanJob) {
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return operand1;
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}
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return applyReverseOperationsDownToHuman((MathOperationJob) job.operand1Job(), operand1);
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}
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private long applyReverseOperationsDownToHumanViaOperand2(
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MathOperationJob job, long lastValue, Long operand1) {
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Long operand2;
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if (job == rootJob) {
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operand2 = operand1;
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} else {
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operand2 = job.applyReverseToFindOperand2(lastValue, operand1);
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}
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if (job.operand2Job() == humanJob) {
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return operand2;
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}
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return applyReverseOperationsDownToHuman((MathOperationJob) job.operand2Job(), operand2);
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}
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}

‎src/main/java/eu/happycoders/adventofcode2022/day21/JobsParser.java‎

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package eu.happycoders.adventofcode2022.day21;
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import java.util.Map;
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import java.util.regex.Matcher;
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import java.util.regex.Pattern;
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import java.util.stream.Collectors;
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class JobsParser {
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private static final Pattern PATTERN_NUMBER_JOB = Pattern.compile("([a-z]{4}): (\\d+)");
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private static final Pattern PATTERN_MATH_OPERATION_JOB =
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Pattern.compile("([a-z]{4}): ([a-z]{4}) ([+-/*]) ([a-z]{4})");
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static Map<String, Job> parse(String input) {
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Map<String, Job> monkeyNameToJob =
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input
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.lines()
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.map(JobsParser::parseJob)
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.collect(Collectors.toMap(Job::monkeyName, job -> job));
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for (Job value : monkeyNameToJob.values()) {
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if (value instanceof MathOperationJob op) {
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op.setOperand1Job(monkeyNameToJob.get(op.operand1MonkeyName()));
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op.setOperand2Job(monkeyNameToJob.get(op.operand2MonkeyName()));
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}
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}
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return monkeyNameToJob;
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}
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private static Job parseJob(String input) {
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Matcher matcher = PATTERN_NUMBER_JOB.matcher(input);
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if (matcher.matches()) {
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String monkeyName = matcher.group(1);
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int value = Integer.parseInt(matcher.group(2));
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return new NumberJob(monkeyName, value);
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}
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matcher = PATTERN_MATH_OPERATION_JOB.matcher(input);
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if (matcher.matches()) {
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String monkeyName = matcher.group(1);
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String operand1MonkeyName = matcher.group(2);
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String operationSymbol = matcher.group(3);
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String operand2MonkeyName = matcher.group(4);
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return switch (operationSymbol) {
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case "+" -> new MathOperationJobAddition(
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monkeyName, operand1MonkeyName, operand2MonkeyName);
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case "-" -> new MathOperationJobSubtraction(
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monkeyName, operand1MonkeyName, operand2MonkeyName);
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case "*" -> new MathOperationJobMultiplication(
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monkeyName, operand1MonkeyName, operand2MonkeyName);
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case "/" -> new MathOperationJobDivision(
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monkeyName, operand1MonkeyName, operand2MonkeyName);
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default -> throw new IllegalStateException("Unknown symbol: " + operationSymbol);
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};
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}
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throw new IllegalStateException("Don't know how to parse: " + input);
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}
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}

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