Initial day 5 implementation

1 files changed, 111 insertions, 0 deletions

diff --git a/src/Day05.kt b/src/Day05.kt
new file mode 100644
index 0000000..fece98e
--- /dev/null
+++ b/src/Day05.kt
@@ -0,0 +1,111 @@
+import kotlin.math.absoluteValue
+import kotlin.math.sign
+
+class Line(val start: Pair<Int, Int>, val end: Pair<Int, Int>) {
+    companion object {
+        fun fromString(input: String): Line {
+            val parts = input.split(" -> ").map { part ->
+                val coordinates = part.split(",").map { it.toInt() }
+                coordinates[0] to coordinates[1]
+            }
+
+            return Line(parts[0], parts[1])
+        }
+    }
+}
+
+fun main() {
+    fun part1(input: List<String>): Int {
+        val lines = input.map(Line::fromString)
+
+        val positions = mutableMapOf<Pair<Int, Int>, Int>()
+        lines.forEach {
+            when {
+                it.start.first == it.end.first -> {
+                    if (it.start.second <= it.end.second) {
+                        for (y in it.start.second..it.end.second) {
+                            positions[it.start.first to y] = 1 + positions.getOrDefault(it.start.first to y, 0)
+                        }
+                    } else {
+                        for (y in it.end.second..it.start.second) {
+                            positions[it.start.first to y] = 1 + positions.getOrDefault(it.start.first to y, 0)
+                        }
+                    }
+                }
+                it.start.second == it.end.second -> {
+                    if (it.start.first<= it.end.first) {
+                        for (x in it.start.first..it.end.first) {
+                            positions[x to it.start.second] = 1 + positions.getOrDefault(x to it.start.second, 0)
+                        }
+                    } else {
+                        for (x in it.end.first..it.start.first) {
+                            positions[x to it.start.second] = 1 + positions.getOrDefault(x to it.start.second, 0)
+                        }
+                    }
+                }
+
+            }
+        }
+
+        return positions.values.count { it >= 2 }
+    }
+
+
+    fun part2(input: List<String>): Int {
+        val lines = input.map(Line::fromString)
+
+        val positions = mutableMapOf<Pair<Int, Int>, Int>()
+        lines.forEach {
+            when {
+                it.start.first == it.end.first -> {
+                    if (it.start.second <= it.end.second) {
+                        for (y in it.start.second..it.end.second) {
+                            positions[it.start.first to y] = 1 + positions.getOrDefault(it.start.first to y, 0)
+                        }
+                    } else {
+                        for (y in it.end.second..it.start.second) {
+                            positions[it.start.first to y] = 1 + positions.getOrDefault(it.start.first to y, 0)
+                        }
+                    }
+                }
+                it.start.second == it.end.second -> {
+                    if (it.start.first<= it.end.first) {
+                        for (x in it.start.first..it.end.first) {
+                            positions[x to it.start.second] = 1 + positions.getOrDefault(x to it.start.second, 0)
+                        }
+                    } else {
+                        for (x in it.end.first..it.start.first) {
+                            positions[x to it.start.second] = 1 + positions.getOrDefault(x to it.start.second, 0)
+                        }
+                    }
+                }
+                (it.end.first - it.start.first).absoluteValue == (it.end.second - it.start.second).absoluteValue -> {
+                    val xOffset = it.end.first - it.start.first
+                    val yOffset = it.end.second - it.start.second
+
+                    val xSign = xOffset.sign
+                    val ySign = yOffset.sign
+
+                    val length = xOffset.absoluteValue
+
+                    for (i in 0..length) {
+                        val x = it.start.first + xSign * i
+                        val y = it.start.second + ySign * i
+                        positions[x to y] = 1 + positions.getOrDefault(x to y, 0)
+                    }
+
+                }
+            }
+        }
+
+        return positions.values.count { it >= 2 }
+    }
+
+    val testInput = readInputAsLines("Day05_test")
+    check(part1(testInput) == 5)
+    check(part2(testInput) == 12)
+
+    val input = readInputAsLines("Day05")
+    println(part1(input))
+    println(part2(input))
+}