java: add solutions for year 2016, day 15

java/src/benchmark/java/com/github/saser/adventofcode/year2016/day15/BUILD.bazel

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+java_library(
+    name = "benchmark_library",
+    srcs = glob(["*.java"]),
+    deps = [
+        "@maven//:org_openjdk_jmh_jmh_core",
+        "//java/src/main/java/com/github/saser/adventofcode/year2016/day15:day15",
+    ],
+    plugins = ["//java/src/benchmark:annotation_processor"],
+    data = ["//inputs:2016/15"],
+)
+
+java_binary(
+    name = "benchmark",
+    main_class = "org.openjdk.jmh.Main",
+    runtime_deps = [
+        "@maven//:org_openjdk_jmh_jmh_core",
+        ":benchmark_library",
+    ],
+)

java/src/benchmark/java/com/github/saser/adventofcode/year2016/day15/Day15Benchmark.java

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+package com.github.saser.adventofcode.year2016.day15;
+
+import java.io.IOException;
+import java.io.Reader;
+import java.io.StringReader;
+import java.nio.file.Files;
+import java.nio.file.FileSystems;
+import java.util.concurrent.TimeUnit;
+
+import org.openjdk.jmh.annotations.Benchmark;
+import org.openjdk.jmh.annotations.BenchmarkMode;
+import org.openjdk.jmh.annotations.Fork;
+import org.openjdk.jmh.annotations.Measurement;
+import org.openjdk.jmh.annotations.Mode;
+import org.openjdk.jmh.annotations.OutputTimeUnit;
+import org.openjdk.jmh.annotations.Scope;
+import org.openjdk.jmh.annotations.Setup;
+import org.openjdk.jmh.annotations.State;
+import org.openjdk.jmh.annotations.TearDown;
+import org.openjdk.jmh.annotations.Warmup;
+
+@BenchmarkMode(Mode.AverageTime)
+@Fork(1)
+@Measurement(iterations = 1, time = 1)
+@OutputTimeUnit(TimeUnit.MILLISECONDS)
+@State(Scope.Benchmark)
+@Warmup(iterations = 5, time = 1)
+public class Day15Benchmark {
+    private Reader input;
+
+    @Setup
+    public void setup() throws IOException {
+        var path = FileSystems.getDefault().getPath("inputs", "2016", "15");
+        var contents = Files.readString(path);
+        this.input = new StringReader(contents);
+    }
+
+    @Benchmark
+    public void part1() throws IOException {
+        Day15.part1(this.input);
+        this.input.reset();
+    }
+
+    @Benchmark
+    public void part2() throws IOException {
+        Day15.part2(this.input);
+        this.input.reset();
+    }
+}

java/src/main/java/com/github/saser/adventofcode/year2016/day15/BUILD.bazel

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+package(default_visibility = ["//visibility:public"])
+
+java_library(
+    name = "day15",
+    srcs = glob(["*.java"]),
+    deps = [
+        "//java/src/main/java/com/github/saser/adventofcode/tuple:tuple",
+        "//java/src/main/java/com/github/saser/adventofcode:adventofcode",
+    ],
+)

java/src/main/java/com/github/saser/adventofcode/year2016/day15/Day15.java

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+package com.github.saser.adventofcode.year2016.day15;
+
+import java.io.BufferedReader;
+import java.io.Reader;
+import java.util.Set;
+import java.util.regex.Pattern;
+import java.util.stream.Collectors;
+
+import com.github.saser.adventofcode.Result;
+import com.github.saser.adventofcode.tuple.Tuple2;
+import com.github.saser.adventofcode.tuple.Tuple3;
+
+public final class Day15 {
+    public static Result part1(Reader r) {
+        return solve(r, 1);
+    }
+
+    public static Result part2(Reader r) {
+        return solve(r, 2);
+    }
+
+    private static Result solve(Reader r, int part) {
+        var discs = Day15.parse(r);
+        if (part == 2) {
+            discs.add(new Tuple3<>(discs.size() + 1L, 11L, 0L));
+        }
+        var equations = discs.stream()
+                .map(tuple -> {
+                    var disc = tuple.v1;
+                    var mod = tuple.v2;
+                    var position = tuple.v3;
+                    var a = Day15.posMod(-(position + disc), mod);
+                    return new Tuple2<>(a, mod);
+                })
+                .collect(Collectors.toSet());
+        var x = Day15.crt(equations);
+        return Result.ok(Long.toString(x));
+    }
+
+    private static Set<Tuple3<Long, Long, Long>> parse(Reader r) {
+        var re = Pattern.compile("Disc #(\\d+) has (\\d+) positions; at time=0, it is at position (\\d+).");
+        return new BufferedReader(r)
+                .lines()
+                .map(line -> {
+                    var matcher = re.matcher(line);
+                    if (!matcher.matches()) {
+                        throw new IllegalArgumentException(String.format("invalid line: %s", line));
+                    }
+                    var disc = Long.parseLong(matcher.group(1));
+                    var mod = Long.parseLong(matcher.group(2));
+                    var position = Long.parseLong(matcher.group(3));
+                    return new Tuple3<>(disc, mod, position);
+                })
+                .collect(Collectors.toSet());
+    }
+
+    private static long crt(Set<Tuple2<Long, Long>> equations) {
+        var it = equations.iterator();
+        var acc = it.next();
+        while (it.hasNext()) {
+            var next = it.next();
+            acc = Day15.crt(acc, next);
+        }
+        var x = acc.v1;
+        var n = acc.v2;
+        return Day15.posMod(x, n);
+    }
+
+    private static Tuple2<Long, Long> crt(Tuple2<Long, Long> an1, Tuple2<Long, Long> an2) {
+        var a1 = an1.v1;
+        var n1 = an1.v2;
+        var a2 = an2.v1;
+        var n2 = an2.v2;
+        var m1m2 = Day15.eea(n1, n2);
+        var m1 = m1m2.v2;
+        var m2 = m1m2.v3;
+        var x = a1 * m2 * n2 + a2 * m1 * n1;
+        var n1n2 = n1 * n2;
+        return new Tuple2<>(Day15.posMod(x, n1n2), n1n2);
+    }
+
+    private static Tuple3<Long, Long, Long> eea(long a, long b) {
+        return eea(a, b, 1, 0, 0, 1);
+    }
+
+    private static Tuple3<Long, Long, Long> eea(long r0, long r1, long s0, long s1, long t0, long t1) {
+        if (r1 == 0) {
+            return new Tuple3<>(r0, s0, t0);
+        }
+        var q = r0 / r1;
+        return eea(r1, r0 - q * r1, s1, s0 - q * s1, t1, t0 - q * t1);
+    }
+
+    private static long posMod(long a, long n) {
+        var r = a % n;
+        if (r < 0) {
+            r += n;
+        }
+        return r;
+    }
+}

java/src/test/java/com/github/saser/adventofcode/year2016/day15/BUILD.bazel

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+java_test(
+    name = "test",
+    srcs = glob(["*.java"]),
+    test_class = "com.github.saser.adventofcode.year2016.day15.Day15Test",
+    resources = ["//java/src/test/resources/com/github/saser/adventofcode/year2016/day15:testdata"],
+    deps = [
+        "@maven//:junit_junit",
+        "//java/src/main/java/com/github/saser/adventofcode:adventofcode",
+        "//java/src/main/java/com/github/saser/adventofcode/year2016/day15:day15",
+    ],
+    data = ["//inputs:2016/15"],
+)

java/src/test/java/com/github/saser/adventofcode/year2016/day15/Day15Test.java

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+package com.github.saser.adventofcode.year2016.day15;
+
+import java.io.FileReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+import org.junit.Test;
+import org.junit.Assert;
+
+public class Day15Test {
+    @Test
+    public void part1Example() {
+        var input = new InputStreamReader(this.getClass().getResourceAsStream("example"));
+        var output = "5";
+        var result = Day15.part1(input);
+        Assert.assertEquals("no error", "", result.error);
+        Assert.assertEquals("correct output", output, result.answer);
+    }
+
+    @Test
+    public void part1Actual() throws IOException {
+        try (var input = new FileReader("inputs/2016/15")) {
+            var output = "148737";
+            var result = Day15.part1(input);
+            Assert.assertEquals("no error", "", result.error);
+            Assert.assertEquals("correct output", output, result.answer);
+        }
+    }
+
+     @Test
+     public void part2Actual() throws IOException {
+         try (var input = new FileReader("inputs/2016/15")) {
+             var output = "2353212";
+             var result = Day15.part2(input);
+             Assert.assertEquals("no error", "", result.error);
+             Assert.assertEquals("correct output", output, result.answer);
+         }
+     }
+}

java/src/test/resources/com/github/saser/adventofcode/year2016/day15/BUILD.bazel

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+package(default_visibility = ["//visibility:public"])
+
+filegroup(
+    name = "testdata",
+    testonly = 1,
+    srcs = glob(["*"]),
+)

java/src/test/resources/com/github/saser/adventofcode/year2016/day15/example

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+Disc #1 has 5 positions; at time=0, it is at position 4.
+Disc #2 has 2 positions; at time=0, it is at position 1.