1 files changed, 58 insertions, 0 deletions
diff --git a/challenge-281/roger-bell-west/lua/ch-2.lua b/challenge-281/roger-bell-west/lua/ch-2.lua
new file mode 100755
index 0000000000..3979fb2830
--- /dev/null
+++ b/challenge-281/roger-bell-west/lua/ch-2.lua
@@ -0,0 +1,58 @@
+#! /usr/bin/lua
+
+function cs2xy(a)
+   local x = string.byte(a, 1) - string.byte("a")
+   local y = string.byte(a, 2) - string.byte("1")
+   return {x, y}
+end
+
+function knightsmove(from, to)
+   local fc = cs2xy(from)
+   local tc = cs2xy(to)
+   local queue = {}
+   table.insert(queue, {fc[1], fc[2], 0})
+   local seen = {}
+   while #queue > 0 do
+      local cc = table.remove(queue, 1)
+      if (cc[1] == tc[1] and cc[2] == tc[2]) then
+         return cc[3]
+      else
+         for _, offset in ipairs({
+               {2, 1},
+               {1, 2},
+               {2, -1},
+               {1, -2},
+               {-2, 1},
+               {-1, 2},
+               {-2, -1},
+               {-1, -2}
+         }) do
+            local x = cc[1] + offset[1]
+            local y = cc[2] + offset[2]
+            if (x >= 0 and x <= 7 and y >= 0 and y <= 7) then
+               local cv = x * 8 + y
+               if seen[cv] == nil then
+                  table.insert(queue, {x, y, cc[3] + 1})
+                  seen[cv] = true
+               end
+            end
+         end
+      end
+   end
+   return -1
+end
+
+if knightsmove("g2", "a8") == 4 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+io.write(" ")
+
+if knightsmove("g2", "h2") == 3 then
+  io.write("Pass")
+else
+  io.write("FAIL")
+end
+print("")
+