Data commit

Task/M-bius-function/Kotlin/m-bius-function.kotlin

@@ -0,0 +1,58 @@
+import kotlin.math.sqrt
+
+fun main() {
+    println("First 199 terms of the möbius function are as follows:")
+    print("    ")
+    for (n in 1..199) {
+        print("%2d  ".format(mobiusFunction(n)))
+        if ((n + 1) % 20 == 0) {
+            println()
+        }
+    }
+}
+
+private const val MU_MAX = 1000000
+private var MU: IntArray? = null
+
+//  Compute mobius function via sieve
+private fun mobiusFunction(n: Int): Int {
+    if (MU != null) {
+        return MU!![n]
+    }
+
+    //  Populate array
+    MU = IntArray(MU_MAX + 1)
+    val sqrt = sqrt(MU_MAX.toDouble()).toInt()
+    for (i in 0 until MU_MAX) {
+        MU!![i] = 1
+    }
+    for (i in 2..sqrt) {
+        if (MU!![i] == 1) {
+            //  for each factor found, swap + and -
+            for (j in i..MU_MAX step i) {
+                MU!![j] *= -i
+            }
+            //  square factor = 0
+            for (j in i * i..MU_MAX step i * i) {
+                MU!![j] = 0
+            }
+        }
+    }
+    for (i in 2..MU_MAX) {
+        when {
+            MU!![i] == i -> {
+                MU!![i] = 1
+            }
+            MU!![i] == -i -> {
+                MU!![i] = -1
+            }
+            MU!![i] < 0 -> {
+                MU!![i] = 1
+            }
+            MU!![i] > 0 -> {
+                MU!![i] = -1
+            }
+        }
+    }
+    return MU!![n]
+}