September 2017 Update

Task/Dinesmans-multiple-dwelling-problem/Kotlin/dinesmans-multiple-dwelling-problem.kotlin

@@ -0,0 +1,50 @@
+// version 1.1.3
+
+typealias Predicate = (List<String>) -> Boolean
+
+fun <T> permute(input: List<T>): List<List<T>> {
+    if (input.size == 1) return listOf(input)
+    val perms = mutableListOf<List<T>>()
+    val toInsert = input[0]
+    for (perm in permute(input.drop(1))) {
+        for (i in 0..perm.size) {
+            val newPerm = perm.toMutableList()
+            newPerm.add(i, toInsert)
+            perms.add(newPerm)
+        }
+    }
+    return perms
+}
+
+/* looks for for all possible solutions, not just the first */
+fun dinesman(occupants: List<String>, predicates: List<Predicate>) =
+    permute(occupants).filter { perm -> predicates.all { pred -> pred(perm) } }
+
+fun main(args: Array<String>) {
+    val occupants = listOf("Baker", "Cooper", "Fletcher", "Miller", "Smith")
+
+    val predicates = listOf<Predicate>(
+        { it.last() != "Baker" },
+        { it.first() != "Cooper" },
+        { it.last() != "Fletcher" && it.first() != "Fletcher" },
+        { it.indexOf("Miller") > it.indexOf("Cooper") },
+        { Math.abs(it.indexOf("Smith") - it.indexOf("Fletcher")) > 1 },
+        { Math.abs(it.indexOf("Fletcher") - it.indexOf("Cooper")) > 1 }
+    )
+
+    val solutions = dinesman(occupants, predicates)
+    val size = solutions.size
+    if (size == 0) {
+        println("No solutions found")
+    }
+    else {
+        val plural = if (size == 1) "" else "s"
+        println("$size solution$plural found, namely:\n")
+        for (solution in solutions) {
+            for ((i, name) in solution.withIndex()) {
+                println("Floor ${i + 1} -> $name")
+            }
+            println()
+        }
+    }
+}