Initial data commit

Task/N-queens-problem/Lua/n-queens-problem.lua

@@ -0,0 +1,35 @@
+N = 8
+
+-- We'll use nil to indicate no queen is present.
+grid = {}
+for i = 0, N do
+  grid[i] = {}
+end
+
+function can_find_solution(x0, y0)
+  local x0, y0 = x0 or 0, y0 or 1  -- Set default vals (0, 1).
+  for x = 1, x0 - 1 do
+    if grid[x][y0] or grid[x][y0 - x0 + x] or grid[x][y0 + x0 - x] then
+      return false
+    end
+  end
+  grid[x0][y0] = true
+  if x0 == N then return true end
+  for y0 = 1, N do
+    if can_find_solution(x0 + 1, y0) then return true end
+  end
+  grid[x0][y0] = nil
+  return false
+end
+
+if can_find_solution() then
+  for y = 1, N do
+    for x = 1, N do
+      -- Print "|Q" if grid[x][y] is true; "|_" otherwise.
+      io.write(grid[x][y] and "|Q" or "|_")
+    end
+    print("|")
+  end
+else
+  print(string.format("No solution for %d queens.\n", N))
+end