Create shellsort.lua

Author: sirwez

sorting/shellsort.lua

@@ -0,0 +1,31 @@
+local shellsort = {}
+shellsort.__index = shellsort
+
+function shellsort.sort(a, comparator)
+    local N = a:size()
+    local h = 0
+    while h < math.floor(N / 3) do
+        h = h * 3 + 1
+    end
+
+    for step=h,1,-1 do
+        for i=step,(N-1) do
+            for j=i,step,-step do
+                if comparator(a:get(j), a:get(j-step)) < 0 then
+                    shellsort.exchange(a, j, j-step)
+                else
+                    break
+                end
+            end
+        end
+    end
+
+end
+
+function shellsort.exchange(a, i, j)
+    local temp = a:get(i)
+    a:set(i, a:get(j))
+    a:set(j, temp)
+end
+
+return shellsort