Data commit

Task/Evolutionary-algorithm/Swift/evolutionary-algorithm.swift

@@ -0,0 +1,55 @@
+func evolve(
+  to target: String,
+  parent: inout String,
+  mutationRate: Int,
+  copies: Int
+) {
+  var parentFitness: Int {
+    return fitness(target: target, sentence: parent)
+  }
+
+  var generation = 0
+
+  while parent != target {
+    generation += 1
+
+    let bestOfGeneration =
+        (0..<copies)
+          .map({_ in mutate(sentence: parent, rate: mutationRate) })
+          .map({ (fitness(target: target, sentence: $0), $0) })
+          .sorted(by: { $0.0 < $1.0 })
+          .first!
+
+    if bestOfGeneration.0 < parentFitness {
+      print("Gen \(generation) produced better fit. \(bestOfGeneration.1) with fitness \(bestOfGeneration.0)")
+      parent = bestOfGeneration.1
+    }
+  }
+}
+
+func fitness(target: String, sentence: String) -> Int {
+  return zip(target, sentence).filter(!=).count
+}
+
+func mutate(sentence: String, rate: Int) -> String {
+  return String(
+    sentence.map({char in
+      if Int.random(in: 1...100) - rate <= 0 {
+        return "ABCDEFGHIJKLMNOPQRSTUVWXYZ ".randomElement()!
+      } else {
+        return char
+      }
+    })
+  )
+}
+
+let target = "METHINKS IT IS LIKE A WEASEL"
+let copies = 100
+let mutationRate = 20
+
+var start = mutate(sentence: target, rate: 100)
+
+print("target: \(target)")
+print("Gen 0: \(start) with fitness \(fitness(target: target, sentence: start))")
+
+evolve(to: target, parent: &start, mutationRate: mutationRate, copies: 100)