WIP day 21

2024/src/main/kotlin/CharGrid.kt

@@ -6,6 +6,8 @@ class CharGrid(rows: List<String>) : Grid<Char> {
     constructor(width: Int, height: Int, char: Char)
             : this((1..height).map { char.toString().repeat(width) })
 
+    constructor(vararg rows: String) : this(rows.toList())
+
     init {
         assert(rows.all { it.length == width })
     }

2024/src/main/kotlin/day21.kt

@@ -0,0 +1,63 @@
+fun main() {
+    val inputs = listOf(
+        "789A",
+        "540A",
+        "285A",
+        "140A",
+        "189A",
+    )
+
+    val numberPad = CharGrid(
+        "789",
+        "456",
+        "123",
+        " 0A"
+    )
+
+    val robotPad = CharGrid(
+        " ^A",
+        "<v>"
+    )
+
+    println(keySequence("029A", numberPad))
+    println(keySequence(keySequence("029A", numberPad), robotPad))
+    Integer.parseInt()
+    println("029A".toInt())
+
+}
+
+fun keySequence(code: String, pad: CharGrid, start: Char = 'A'): String {
+    var position = pad.find(start) ?: error("Start position not found")
+    val gap = pad.find(' ') ?: error("Gap not found")
+
+    val result = StringBuilder()
+    for (current in code) {
+        val target = pad.find(current) ?: error("Target key not found")
+
+        val dx = target.x - position.x
+        val dy = target.y - position.y
+
+        if (target.y < gap.y) {
+            result.appendMovement(dy, '^', 'v')
+            result.appendMovement(dx, '<', '>')
+        } else {
+            result.appendMovement(dx, '<', '>')
+            result.appendMovement(dy, '^', 'v')
+        }
+
+        result.append('A')
+
+        position = target
+    }
+
+    return result.toString()
+}
+
+fun StringBuilder.appendMovement(amount: Int, less: Char, more: Char): StringBuilder {
+    when {
+        amount < 0 -> repeat(-amount) { append(less) }
+        amount == 0 -> Unit
+        else -> repeat(amount) { append(more) }
+    }
+    return this
+}