Data commit

Task/Entropy/Lua/entropy.lua

@@ -0,0 +1,19 @@
+function log2 (x) return math.log(x) / math.log(2) end
+
+function entropy (X)
+    local N, count, sum, i = X:len(), {}, 0
+    for char = 1, N do
+        i = X:sub(char, char)
+        if count[i] then
+            count[i] = count[i] + 1
+        else
+            count[i] = 1
+        end
+    end
+    for n_i, count_i in pairs(count) do
+        sum = sum + count_i / N * log2(count_i / N)
+    end
+    return -sum
+end
+
+print(entropy("1223334444"))