diff --git a/src/day05/Day05.kt b/src/day05/Day05.kt
new file mode 100644
index 0000000..7b21765
--- /dev/null
+++ b/src/day05/Day05.kt
@@ -0,0 +1,72 @@
+package day05
+
+import readInput
+
+data class Point(val x: Int, val y: Int) {
+    operator fun plus(other: Point): Point = Point(x + other.x, y + other.y)
+    operator fun times(other: Int): Point = Point(other * x, other * y)
+}
+
+data class Vector(val from: Point, val to: Point) {
+    val horizontal: Boolean
+        get() = from.y == to.y
+
+    val vertical: Boolean
+        get() = from.x == to.x
+
+    val horizontalOrVertical: Boolean
+        get() = horizontal || vertical
+
+    private val xs: Iterable<Int>
+        get() = if (from.x <= to.x) (from.x..to.x) else (to.x..from.x).reversed()
+
+    private val ys: Iterable<Int>
+        get() = if (from.y <= to.y) (from.y..to.y) else (to.y..from.y).reversed()
+
+    val points: Iterable<Point>
+        get() = if (horizontalOrVertical) {
+            xs.flatMap { x -> ys.map { y -> Point(x, y) } }
+        } else {
+            xs.zip(ys).map { (x, y) -> Point(x, y) }
+        }
+}
+
+fun readPoint(input: String): Point {
+    val (x, y) = input.split(",").map { it.toInt() }
+    return Point(x, y)
+}
+
+fun readVector(input: String): Vector {
+    val (from, to) = input.split(" -> ")
+    return Vector(readPoint(from), readPoint(to))
+}
+
+fun part1(input: List<Vector>): Int {
+    var points: MutableMap<Point, Int> = mutableMapOf()
+
+    input.filter { it.horizontalOrVertical }
+        .flatMap { it.points }
+        .forEach { points[it] = 1 + points.getOrDefault(it, 0) }
+
+    return points.count { (_, count) -> count >= 2 }
+}
+
+fun part2(input: List<Vector>): Int {
+    var points: MutableMap<Point, Int> = mutableMapOf()
+
+    input.flatMap { it.points }
+        .forEach { points[it] = 1 + points.getOrDefault(it, 0) }
+
+    return points.count { (_, count) -> count >= 2 }
+}
+
+fun main() {
+    val testInput = readInput(5, "test_input").map { readVector(it) }
+    val input = readInput(5, "input").map { readVector(it) }
+
+    check(part1(testInput) == 5)
+    println(part1(input))
+
+    check(part2(testInput) == 12)
+    println(part2(input))
+}
diff --git a/src/day05/test_input.txt b/src/day05/test_input.txt
new file mode 100644
index 0000000..1d4e36d
--- /dev/null
+++ b/src/day05/test_input.txt
@@ -0,0 +1,10 @@
+0,9 -> 5,9
+8,0 -> 0,8
+9,4 -> 3,4
+2,2 -> 2,1
+7,0 -> 7,4
+6,4 -> 2,0
+0,9 -> 2,9
+3,4 -> 1,4
+0,0 -> 8,8
+5,5 -> 8,2
\ No newline at end of file