Data update

Task/Sorting-algorithms-Merge-sort/REXX/sorting-algorithms-merge-sort-2.rexx

@@ -0,0 +1,67 @@
+Main:
+call Generate
+call Show
+call Mergesort 1,n
+call Show
+exit
+
+Generate:
+call Random,,12345
+n = 10
+do i = 1 to n
+   stem.i = Random()
+end
+stem.0 = n
+return
+
+Show:
+do i = 1 to n
+   say right(i,2) right(stem.i,3)
+end
+say
+return
+
+Mergesort:
+procedure expose stem. work.
+arg b,e
+if e-b < 1 then
+   return
+if e-b = 1 then do
+   if stem.b > stem.e then do
+      t = stem.b; stem.b = stem.e; stem.e = t
+   end
+   return
+end
+m = (b+e)%2
+call Mergesort b,m
+call Mergesort m+1,e
+call Merger b,m,e
+return
+
+Merger:
+procedure expose stem. work.
+arg b,m,e
+i = b; j = m+1; k = b
+do while i <= m | j <= e
+   select
+      when i <= m & j <= e then do
+         if stem.i <= stem.j then do
+            work.k = stem.i; i = i+1
+         end
+         else do
+            work.k = stem.j; j = j+1
+         end
+         k = k+1
+      end
+      when i<=m then do
+         work.k = stem.i; i = i+1; k = k+1
+      end
+      otherwise do
+         work.k = stem.j; j = j+1; k = k+1
+      end
+   end
+end
+do i = b to e
+   stem.i = work.i
+end
+return