diff --git a/src/Utils.kt b/src/Utils.kt
index 23dfa16..82e2236 100644
--- a/src/Utils.kt
+++ b/src/Utils.kt
@@ -11,6 +11,7 @@ private fun openFile(day: Int, name: String) = File("src/year%4d/day%02d".format
  */
 fun readInput(day: Int, name: String) = openFile(day, name).readLines()
 
+fun readInputAsString(day: Int, name: String) = openFile(day, name).readText()
 fun readInputAsInts(day: Int, name: String) = readInput(day, name).map { it.toInt() }
 fun readInputAsCommaSeparatedInts(day: Int, name: String) = openFile(day, name)
     .readText()
diff --git a/src/year2021/day19/Day19.kt b/src/year2021/day19/Day19.kt
new file mode 100644
index 0000000..e1d6391
--- /dev/null
+++ b/src/year2021/day19/Day19.kt
@@ -0,0 +1,131 @@
+package year2021.day19
+
+import readInputAsString
+import java.time.Instant
+import java.util.*
+import kotlin.math.absoluteValue
+import kotlin.math.sin
+import kotlin.math.cos
+import kotlin.math.sqrt
+
+data class Vector(val x: Int, val y: Int, val z: Int) {
+    fun magnitude(): Double = sqrt((x * x + y * y + z * z).toDouble())
+    fun translate(by: Vector): Vector = this - by
+    fun rotate(u: Vector, v: Vector, w: Vector): Vector =
+        Vector(
+            u.x * x + v.x * y + w.x * z,
+            u.y * x + v.y * y + w.y * z,
+            u.z * x + v.z * y + w.z * z,
+        )
+
+    operator fun plus(v: Vector): Vector = Vector(x + v.x, y + v.y, z + v.z)
+    operator fun minus(v: Vector): Vector = Vector(x - v.x, y - v.y, z - v.z)
+    operator fun unaryMinus(): Vector = Vector(-x, -y, -z)
+    operator fun times(c: Int): Vector = Vector(c * x, c * y, c * z)
+}
+
+data class Scanner(val beacons: Set<Vector>)
+
+// region parsing
+fun String.toVector() =
+    this.split(",").map(String::toInt).let { (x, y, z) ->
+        Vector(x, y, z)
+    }
+
+fun String.toScanner() =
+    Scanner(this.split("\n").drop(1).map(String::toVector).toSet())
+// endregion
+
+// region constants
+val TRIGONOMETRY: Set<Pair<Int, Int>> =
+    listOf(0, 90, 180, 270)
+        .map { Math.toRadians(it.toDouble()) }
+        .map { sin(it).toInt() to cos(it).toInt() }
+        .toSet()
+
+val ROTATIONS: Set<Triple<Vector, Vector, Vector>> =
+    TRIGONOMETRY
+        .flatMap { alpha -> TRIGONOMETRY.flatMap { beta -> TRIGONOMETRY.map { gamma -> Triple(alpha, beta, gamma) } } }
+        .map { (a, b, g) ->
+            val (sinA, cosA) = a
+            val (sinB, cosB) = b
+            val (sinG, cosG) = g
+
+            Triple(
+                Vector(cosA * cosB, sinA * cosB, -sinB),
+                Vector(cosA * sinB * sinG - sinA * cosG, sinA * sinB * sinG + cosA * cosG, cosB * sinG),
+                Vector(cosA * sinB * cosG + sinA * sinG, sinA * sinB * cosG - cosA * sinG, cosB * cosG)
+            )
+        }
+        .toSet()
+// endregion
+
+fun checkOverlap(beacons: Set<Vector>, scanner: Scanner): Pair<Vector, List<Vector>>? {
+    ROTATIONS.forEach { (u, v, w) ->
+        val rotatedBeacons = scanner.beacons.map { it.rotate(u, v, w) }
+
+        beacons.forEach { anchor -> // anchor from already located beacons
+            val translateWithRegardsToAnchor = beacons.map { it.translate(anchor) }.toSet()
+            rotatedBeacons.forEach { rotatedAnchor ->
+                val translateWithRegardsToRotatedAnchor = rotatedBeacons.map { it.translate(rotatedAnchor) }.toSet()
+
+                val intersect = translateWithRegardsToAnchor.intersect(translateWithRegardsToRotatedAnchor)
+                if (intersect.size >= 12) {
+                    val scannerPosition = rotatedAnchor - anchor
+                    val translatedBeacons = rotatedBeacons.map { it - rotatedAnchor + anchor }
+                    return scannerPosition to translatedBeacons
+                }
+            }
+        }
+    }
+
+    return null
+}
+
+fun locate(scanners: List<Scanner>): Pair<Set<Vector>, Set<Vector>> {
+    val beacons = mutableSetOf<Vector>()
+    val scannerPositions = mutableSetOf<Vector>()
+
+    // add first scanner that is used as anchor
+    beacons.addAll(scanners.first().beacons)
+
+    val remainingScanners = scanners.drop(1).toMutableList()
+    while (remainingScanners.isNotEmpty()) {
+        for (i in remainingScanners.indices.reversed()) {
+            val (scannerPosition, translatedBeacons) = checkOverlap(beacons, remainingScanners[i]) ?: continue
+
+            beacons.addAll(translatedBeacons)
+            scannerPositions.add(scannerPosition)
+            remainingScanners.removeAt(i)
+            println("Done: ${scanners.size - remainingScanners.size}/${scanners.size}")
+        }
+    }
+
+    return scannerPositions to beacons
+}
+
+fun part1(input: Set<Vector>): Int = input.size
+
+fun part2(input: Set<Vector>): Int =
+    input.maxOf { a ->
+        input.maxOf { b ->
+            (a.x - b.x).absoluteValue + (a.y - b.y).absoluteValue + (a.z - b.z).absoluteValue
+        }
+    }
+
+fun main() {
+    val sample =
+        readInputAsString(19, "sample").split("\n\n").map(String::toScanner)
+    val input =
+        readInputAsString(19, "input").split("\n\n").map(String::toScanner)
+
+    println(Date.from(Instant.now()))
+    val (sampleScanners, sampleBeacons) = locate(sample)
+    check(part1(sampleBeacons) == 79)
+    check(part2(sampleScanners) == 3621)
+
+    val (inputScanners, inputBeacons) = locate(input)
+    println(part1(inputBeacons))
+    println(part2(inputScanners))
+    println(Date.from(Instant.now()))
+}
diff --git a/src/year2021/day19/sample.txt b/src/year2021/day19/sample.txt
new file mode 100644
index 0000000..b596cc4
--- /dev/null
+++ b/src/year2021/day19/sample.txt
@@ -0,0 +1,136 @@
+--- scanner 0 ---
+404,-588,-901
+528,-643,409
+-838,591,734
+390,-675,-793
+-537,-823,-458
+-485,-357,347
+-345,-311,381
+-661,-816,-575
+-876,649,763
+-618,-824,-621
+553,345,-567
+474,580,667
+-447,-329,318
+-584,868,-557
+544,-627,-890
+564,392,-477
+455,729,728
+-892,524,684
+-689,845,-530
+423,-701,434
+7,-33,-71
+630,319,-379
+443,580,662
+-789,900,-551
+459,-707,401
+
+--- scanner 1 ---
+686,422,578
+605,423,415
+515,917,-361
+-336,658,858
+95,138,22
+-476,619,847
+-340,-569,-846
+567,-361,727
+-460,603,-452
+669,-402,600
+729,430,532
+-500,-761,534
+-322,571,750
+-466,-666,-811
+-429,-592,574
+-355,545,-477
+703,-491,-529
+-328,-685,520
+413,935,-424
+-391,539,-444
+586,-435,557
+-364,-763,-893
+807,-499,-711
+755,-354,-619
+553,889,-390
+
+--- scanner 2 ---
+649,640,665
+682,-795,504
+-784,533,-524
+-644,584,-595
+-588,-843,648
+-30,6,44
+-674,560,763
+500,723,-460
+609,671,-379
+-555,-800,653
+-675,-892,-343
+697,-426,-610
+578,704,681
+493,664,-388
+-671,-858,530
+-667,343,800
+571,-461,-707
+-138,-166,112
+-889,563,-600
+646,-828,498
+640,759,510
+-630,509,768
+-681,-892,-333
+673,-379,-804
+-742,-814,-386
+577,-820,562
+
+--- scanner 3 ---
+-589,542,597
+605,-692,669
+-500,565,-823
+-660,373,557
+-458,-679,-417
+-488,449,543
+-626,468,-788
+338,-750,-386
+528,-832,-391
+562,-778,733
+-938,-730,414
+543,643,-506
+-524,371,-870
+407,773,750
+-104,29,83
+378,-903,-323
+-778,-728,485
+426,699,580
+-438,-605,-362
+-469,-447,-387
+509,732,623
+647,635,-688
+-868,-804,481
+614,-800,639
+595,780,-596
+
+--- scanner 4 ---
+727,592,562
+-293,-554,779
+441,611,-461
+-714,465,-776
+-743,427,-804
+-660,-479,-426
+832,-632,460
+927,-485,-438
+408,393,-506
+466,436,-512
+110,16,151
+-258,-428,682
+-393,719,612
+-211,-452,876
+808,-476,-593
+-575,615,604
+-485,667,467
+-680,325,-822
+-627,-443,-432
+872,-547,-609
+833,512,582
+807,604,487
+839,-516,451
+891,-625,532
+-652,-548,-490
+30,-46,-14
\ No newline at end of file