Data commit

Task/Aliquot-sequence-classifications/Kotlin/aliquot-sequence-classifications.kotlin

@@ -0,0 +1,62 @@
+// version 1.1.3
+
+data class Classification(val sequence: List<Long>, val aliquot: String)
+
+const val THRESHOLD = 1L shl 47
+
+fun sumProperDivisors(n: Long): Long {
+    if (n < 2L) return 0L
+    val sqrt = Math.sqrt(n.toDouble()).toLong()
+    var sum = 1L + (2L..sqrt)
+        .filter { n % it == 0L }
+        .map { it + n / it }
+        .sum()
+    if (sqrt * sqrt == n) sum -= sqrt
+    return sum
+}
+
+fun classifySequence(k: Long): Classification {
+    require(k > 0)
+    var last = k
+    val seq = mutableListOf(k)
+    while (true) {
+        last = sumProperDivisors(last)
+        seq.add(last)
+        val n = seq.size
+        val aliquot = when {
+            last == 0L                  -> "Terminating"
+            n == 2 && last == k         -> "Perfect"
+            n == 3 && last == k         -> "Amicable"
+            n >= 4 && last == k         -> "Sociable[${n - 1}]"
+            last == seq[n - 2]          -> "Aspiring"
+            last in seq.slice(1..n - 3) -> "Cyclic[${n - 1 - seq.indexOf(last)}]"
+            n == 16 || last > THRESHOLD -> "Non-Terminating"
+            else                        -> ""
+        }
+        if (aliquot != "") return Classification(seq, aliquot)
+    }
+}
+
+fun main(args: Array<String>) {
+    println("Aliqot classifications - periods for Sociable/Cyclic in square brackets:\n")
+    for (k in 1L..10) {
+        val (seq, aliquot) = classifySequence(k)
+        println("${"%2d".format(k)}: ${aliquot.padEnd(15)} $seq")
+    }
+
+    val la = longArrayOf(
+        11, 12, 28, 496, 220, 1184, 12496, 1264460, 790, 909, 562, 1064, 1488
+    )
+    println()
+
+    for (k in la) {
+        val (seq, aliquot) = classifySequence(k)
+        println("${"%7d".format(k)}: ${aliquot.padEnd(15)} $seq")
+    }
+
+    println()
+
+    val k = 15355717786080L
+    val (seq, aliquot) = classifySequence(k)
+    println("$k: ${aliquot.padEnd(15)} $seq")
+}