Move subproject to avoid IntelliJ module name issues

1 files changed, 62 insertions, 0 deletions

diff --git a/aoc-2021-kotlin/src/Day05.kt b/aoc-2021-kotlin/src/Day05.kt
new file mode 100644
index 0000000..2c5e219
--- /dev/null
+++ b/aoc-2021-kotlin/src/Day05.kt
@@ -0,0 +1,62 @@
+import kotlin.math.absoluteValue
+import kotlin.math.max
+import kotlin.math.sign
+
+object Day05 {
+    private data class Line(val start: Pos2D, val end: Pos2D) {
+        companion object {
+            fun fromString(input: String): Line {
+                val (start, end) = input.split(" -> ").map { coordinateString ->
+                    val (x, y) = coordinateString.split(",").map(String::toInt)
+                    Pos2D(x, y)
+                }
+
+                return Line(start, end)
+            }
+        }
+
+        val isHorizontalOrVertical: Boolean
+            get() = start.x == end.x || start.y == end.y
+
+        val isDiagonal: Boolean
+            get() = (end.x - start.x).absoluteValue == (end.y - start.y).absoluteValue
+
+        val pointSequence: Sequence<Pos2D>
+            get() = sequence {
+                val xOffset = end.x - start.x
+                val yOffset = end.y - start.y
+
+                for (s in 0..max(xOffset.absoluteValue, yOffset.absoluteValue)) {
+                    val x = start.x + s * xOffset.sign
+                    val y = start.y + s * yOffset.sign
+
+                    yield(Pos2D(x, y))
+                }
+            }
+    }
+
+    private fun helper(input: List<String>, linePredicate: (line: Line) -> Boolean) = input
+        .asSequence()
+        .map(Line::fromString)
+        .filter(linePredicate)
+        .flatMap(Line::pointSequence)
+        .groupingBy { it }
+        .eachCount()
+        .values
+        .count { it >= 2 }
+
+    fun part1(input: List<String>): Int = helper(input, Line::isHorizontalOrVertical)
+
+    fun part2(input: List<String>): Int = helper(input) { it.isHorizontalOrVertical || it.isDiagonal }
+
+}
+
+fun main() {
+    val testInput = readInputAsLines("Day05_test")
+    check(Day05.part1(testInput) == 5)
+    check(Day05.part2(testInput) == 12)
+
+    val input = readInputAsLines("Day05")
+    println(Day05.part1(input))
+    println(Day05.part2(input))
+}