Ch82 (Lua): Task 2

2 files changed, 39 insertions, 0 deletions

diff --git a/challenge-082/tyler-wardhaugh/lua/ch-2.lua b/challenge-082/tyler-wardhaugh/lua/ch-2.lua
new file mode 100755
index 0000000000..b92e26bffd
--- /dev/null
+++ b/challenge-082/tyler-wardhaugh/lua/ch-2.lua
@@ -0,0 +1,30 @@
+#!/usr/bin/env lua
+
+local t2 = {}
+
+function t2.interleave_string(a, b, c)
+  if a:len() == 0 then return b == c end
+  if b:len() == 0 then return a == c end
+  if c:len() ~= a:len() + b:len() then return end
+
+  -- get heads (1st char) and tails (the rest)
+  local ah, at = a:match("^(%a)(%a*)$")
+  local bh, bt = b:match("^(%a)(%a*)$")
+  local ch, ct = c:match("^(%a)(%a*)$")
+
+  return ((ah == ch) and t2.interleave_string(at, b, ct))
+      or ((bh == ch) and t2.interleave_string(a, bt, ct))
+end
+
+function t2.run(args)
+  if #args ~= 3 then
+    io.stderr:write("error: must supply three strings\n")
+    os.exit(2)
+  end
+
+  local a, b, c = table.unpack(args, 1, 3)
+  local result = t2.interleave_string(a, b, c)
+  if result then print(1) else print(0) end
+end
+
+return t2
diff --git a/challenge-082/tyler-wardhaugh/lua/test.lua b/challenge-082/tyler-wardhaugh/lua/test.lua
index 23b3a4e063..20f0d33d27 100755
--- a/challenge-082/tyler-wardhaugh/lua/test.lua
+++ b/challenge-082/tyler-wardhaugh/lua/test.lua
@@ -9,3 +9,12 @@ describe("Task 1, Common Factors", function()
     assert.are.same(t1.common_factors(18, 23), {1})
   end)
 end)
+
+describe("Task 2, Interleave Strings", function()
+  local t2 = require'ch-2'
+  it("produces correct results for the examples", function()
+    assert.are.same(t2.interleave_string("XY", "X", "XXY"), true)
+    assert.are.same(t2.interleave_string("XXY", "XXZ", "XXXXZY"), true)
+    assert.are.same(t2.interleave_string("YX", "X", "XXY"), false)
+  end)
+end)