Data update

Task/Evolutionary-algorithm/Crystal/evolutionary-algorithm.cr

@@ -0,0 +1,33 @@
+TARGET = "METHINKS IT IS LIKE A WEASEL".chars
+ALPHABET = ('A'..'Z').to_a << ' '
+C = 200
+RATE = 0.05
+
+def fitness (current, target)
+  current.zip(target).count {|a, b| a == b } / current.size
+end
+
+def mutate (current, rate)
+  current.map {|ch| Random.rand < rate ? ALPHABET.sample : ch }
+end
+
+def next_parent (current, target, c, rate)
+  candidate = current
+  candidate_fitness = fitness(current, target)
+  c.times do
+    child = mutate(current, rate)
+    child_fitness = fitness(child, target)
+    if child_fitness > candidate_fitness
+      candidate, candidate_fitness = child, child_fitness
+    end
+  end
+  candidate
+end
+
+parent = TARGET.map { ALPHABET.sample }
+
+(1..).each do |gen|
+  printf "%4d  %s\n", gen, parent.join
+  break if parent == TARGET
+  parent = next_parent(parent, TARGET, C, RATE)
+end