Example solution and stub

exercises/practice/dominoes/.meta/example.lua

@@ -0,0 +1,35 @@
+local function reversed(domino)
+  return { domino[2], domino[1] }
+end
+
+local function without_domino(dominoes, target)
+  local without = {}
+  for i = 1, #dominoes do
+    if i ~= target then
+      table.insert(without, dominoes[i])
+    end
+  end
+  return without
+end
+
+local function can_chain(dominoes)
+  local function recur(left, dominoes, right)
+    if #dominoes == 0 then
+      return left == right
+    end
+
+    for i, domino in ipairs(dominoes) do
+      for _, domino in ipairs({ domino, reversed(domino) }) do
+        if domino[1] == left and recur(domino[2], without_domino(dominoes, i), right) then
+          return true
+        end
+      end
+    end
+
+    return false
+  end
+
+  return recur((dominoes[1] or {})[1], without_domino(dominoes, 1), (dominoes[1] or {})[2])
+end
+
+return { can_chain = can_chain }

exercises/practice/dominoes/dominoes.lua

@@ -0,0 +1,5 @@
+local function can_chain(dominoes)
+
+end
+
+return { can_chain = can_chain }