Data commit

Task/Caesar-cipher/Lua/caesar-cipher-1.lua

@@ -0,0 +1,30 @@
+local function encrypt(text, key)
+	return text:gsub("%a", function(t)
+			local base = (t:lower() == t and string.byte('a') or string.byte('A'))
+
+			local r = t:byte() - base
+			r = r + key
+			r = r%26 -- works correctly even if r is negative
+			r = r + base
+			return string.char(r)
+		end)
+end
+
+local function decrypt(text, key)
+	return encrypt(text, -key)
+end
+
+caesar = {
+	encrypt = encrypt,
+	decrypt = decrypt,
+}
+
+-- test
+do
+	local text = "ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuvwxyz"
+	local encrypted = caesar.encrypt(text, 7)
+	local decrypted = caesar.decrypt(encrypted, 7)
+	print("Original text:  ", text)
+	print("Encrypted text: ", encrypted)
+	print("Decrypted text: ", decrypted)
+end

Task/Caesar-cipher/Lua/caesar-cipher-2.lua

@@ -0,0 +1,32 @@
+local memo = {}
+
+local function make_table(k)
+    local t = {}
+    local a, A = ('a'):byte(), ('A'):byte()
+
+    for i = 0,25 do
+        local  c = a + i
+        local  C = A + i
+        local rc = a + (i+k) % 26
+        local RC = A + (i+k) % 26
+        t[c], t[C] = rc, RC
+    end
+
+    return t
+end
+
+local function caesar(str, k, decode)
+    k = (decode and -k or k) % 26
+
+    local t = memo[k]
+    if not t then
+        t = make_table(k)
+        memo[k] = t
+    end
+
+    local res_t = { str:byte(1,-1) }
+    for i,c in ipairs(res_t) do
+        res_t[i] = t[c] or c
+    end
+    return string.char(unpack(res_t))
+end