adventofcode/src/main/java/AoC2020_15.java at main · pareronia/adventofcode · GitHub

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import com.github.pareronia.aoc.solution.Sample;

import com.github.pareronia.aoc.solution.Samples;

import com.github.pareronia.aoc.solution.SolutionBase;

import java.util.Arrays;

import java.util.List;

import java.util.stream.Stream;

@SuppressWarnings({"PMD.ClassNamingConventions", "PMD.NoPackage"})

public final class AoC2020_15 extends SolutionBase<List<Integer>, Integer, Integer> {

private AoC2020_15(final boolean debug) {

super(debug);

}

public static AoC2020_15 create() {

return new AoC2020_15(false);

}

public static AoC2020_15 createDebug() {

return new AoC2020_15(true);

}

@Override

protected List<Integer> parseInput(final List<String> inputs) {

return Stream.of(inputs.getFirst().split(",")).map(Integer::valueOf).toList();

}

private int play(final List<Integer> numbers, final int numberOfTurns) {

final int[] last = new int[numberOfTurns];

Arrays.fill(last, -1);

for (int i = 0; i < numbers.size() - 1; i++) {

last[numbers.get(i)] = i + 1;

}

int prev = numbers.getLast();

for (int i = numbers.size(); i < numberOfTurns; i++) {

final int prevPrev = last[prev];

last[prev] = i;

prev = prevPrev == -1 ? 0 : i - prevPrev;

}

return prev;

}

@Override

public Integer solvePart1(final List<Integer> numbers) {

return play(numbers, 2020);

}

@Override

public Integer solvePart2(final List<Integer> numbers) {

return play(numbers, 30_000_000);

}

@SuppressWarnings("PMD.AvoidDuplicateLiterals")

@Samples({

@Sample(method = "part1", input = "0,3,6", expected = "436"),

@Sample(method = "part1", input = "1,3,2", expected = "1"),

@Sample(method = "part1", input = "2,1,3", expected = "10"),

@Sample(method = "part1", input = "1,2,3", expected = "27"),

@Sample(method = "part1", input = "2,3,1", expected = "78"),

@Sample(method = "part1", input = "3,2,1", expected = "438"),

@Sample(method = "part1", input = "3,1,2", expected = "1836"),

@Sample(method = "part2", input = "0,3,6", expected = "175594"),

@Sample(method = "part2", input = "1,3,2", expected = "2578"),

@Sample(method = "part2", input = "2,1,3", expected = "3544142"),

@Sample(method = "part2", input = "1,2,3", expected = "261214"),

@Sample(method = "part2", input = "2,3,1", expected = "6895259"),

@Sample(method = "part2", input = "3,2,1", expected = "18"),

@Sample(method = "part2", input = "3,1,2", expected = "362"),

})

public static void main(final String[] args) throws Exception {

create().run();

}

adventofcode/src/main/java/AoC2020_15.java at main · pareronia/adventofcode · GitHub

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