CDE

Task/Evolutionary-algorithm/D/evolutionary-algorithm-1.d

@@ -0,0 +1,33 @@
+import std.stdio, std.random, std.algorithm, std.range, std.ascii;
+
+void evolve(string target, double prob=0.05, int C=100) {
+    auto chars = uppercase ~ " ";
+    char rndCh() { return chars[uniform(0, $)]; }
+    void mutate(char[] parent, char[] child) {
+        foreach (i, ref c; child)
+            c = uniform(0.0, 1.0) < prob ? rndCh() : parent[i];
+    }
+    int fitness(char[] subject, string target) {
+        return count!q{ a[0] != a[1] }(zip(subject, target));
+    }
+    auto parent= map!(i => rndCh())(target).array();
+    auto best = parent.dup;
+    auto child = new char[target.length];
+    int currDist = fitness(parent, target);
+    for (int gen; currDist > 0; gen++) {
+        foreach (_; 0 .. C) {
+            mutate(parent, child);
+            int dist = fitness(child, target);
+            if (dist < currDist) {
+                currDist = dist;
+                best[] = child[];
+            }
+        }
+        parent = best;
+        writefln("Generation %2s, dist=%2s: %s", gen, currDist, best);
+    }
+}
+
+void main() {
+    evolve("METHINKS IT IS LIKE A WEASEL");
+}