June 2018 Update

Task/Percolation-Mean-cluster-density/Kotlin/percolation-mean-cluster-density.kotlin

@@ -0,0 +1,80 @@
+// version 1.2.10
+
+import java.util.Random
+
+val rand = Random()
+const val RAND_MAX = 32767
+
+lateinit var map: IntArray
+var w = 0
+var ww = 0
+
+const val ALPHA = "+.ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
+const val ALEN = ALPHA.length - 3
+
+fun makeMap(p: Double) {
+    val thresh = (p * RAND_MAX).toInt()
+    ww = w * w
+    var i = ww
+    map = IntArray(i)
+    while (i-- != 0) {
+        val r = rand.nextInt(RAND_MAX + 1)
+        if (r < thresh) map[i] = -1
+    }
+}
+
+fun showCluster() {
+    var k = 0
+    for (i in 0 until w) {
+        for (j in 0 until w) {
+            val s = map[k++]
+            val c = if (s < ALEN) ALPHA[1 + s] else '?'
+            print(" $c")
+        }
+        println()
+    }
+}
+
+fun recur(x: Int, v: Int) {
+    if ((x in 0 until ww) && map[x] == -1) {
+        map[x] = v
+        recur(x - w, v)
+        recur(x - 1, v)
+        recur(x + 1, v)
+        recur(x + w, v)
+    }
+}
+
+fun countClusters(): Int {
+    var cls = 0
+    for (i in 0 until ww) {
+        if (map[i] != -1) continue
+        recur(i, ++cls)
+    }
+    return cls
+}
+
+fun tests(n: Int, p: Double): Double {
+    var k = 0.0
+    for (i in 0 until n) {
+        makeMap(p)
+        k += countClusters().toDouble() / ww
+    }
+    return k / n
+}
+
+fun main(args: Array<String>) {
+    w = 15
+    makeMap(0.5)
+    val cls = countClusters()
+    println("width = 15, p = 0.5, $cls clusters:")
+    showCluster()
+
+    println("\np = 0.5, iter = 5:")
+    w = 1 shl 2
+    while (w <= 1 shl 13) {
+        val t = tests(5, 0.5)
+        println("%5d %9.6f".format(w, t))
+        w = w shl 1
+    }
+}