Data commit

Task/Evolutionary-algorithm/Lua/evolutionary-algorithm.lua

@@ -0,0 +1,52 @@
+local target = "METHINKS IT IS LIKE A WEASEL"
+local alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ "
+local c, p = 100, 0.06
+
+local function fitness(s)
+	local score = #target
+	for i = 1,#target do
+		if s:sub(i,i) == target:sub(i,i) then score = score - 1 end
+	end
+	return score
+end
+
+local function mutate(s, rate)
+	local result, idx = ""
+	for i = 1,#s do
+		if math.random() < rate then
+			idx = math.random(#alphabet)
+			result = result .. alphabet:sub(idx,idx)
+		else
+			result = result .. s:sub(i,i)
+		end
+	end
+	return result, fitness(result)
+end
+
+local function randomString(len)
+	local result, idx = ""
+	for i = 1,len do
+		idx = math.random(#alphabet)
+		result = result .. alphabet:sub(idx,idx)
+	end
+	return result
+end
+
+local function printStep(step, s, fit)
+	print(string.format("%04d: ", step) .. s .. " [" .. fit .."]")
+end
+
+math.randomseed(os.time())
+local parent = randomString(#target)
+printStep(0, parent, fitness(parent))
+
+local step = 0
+while parent ~= target do
+	local bestFitness, bestChild, child, fitness = #target + 1
+	for i = 1,c do
+		child, fitness = mutate(parent, p)
+		if fitness < bestFitness then bestFitness, bestChild = fitness, child end
+	end
+	parent, step = bestChild, step + 1
+	printStep(step, parent, bestFitness)
+end