tasks a-s

Task/Run-length-encoding/Lua/run-length-encoding.lua

@@ -0,0 +1,31 @@
+local C, Ct, R, Cf, Cc = lpeg.C, lpeg.Ct, lpeg.R, lpeg.Cf, lpeg.Cc
+astable = Ct(C(1)^0)
+
+function compress(t)
+    local ret = {}
+    for i, v in ipairs(t) do
+      if t[i-1] and v == t[i-1] then
+        ret[#ret - 1] = ret[#ret - 1] + 1
+      else
+        ret[#ret + 1] = 1
+        ret[#ret + 1] = v
+      end
+    end
+    t = ret
+    return table.concat(ret)
+end
+q = io.read()
+print(compress(astable:match(q)))
+
+undo = Ct((Cf(Cc"0" * C(R"09")^1, function(a, b) return 10 * a + b end) * C(R"AZ"))^0)
+
+function decompress(s)
+  t = undo:match(s)
+  local ret = ""
+  for i = 1, #t - 1, 2 do
+    for _ = 1, t[i] do
+      ret = ret .. t[i+1]
+    end
+  end
+  return ret
+end