A-M baby

Task/Find-the-missing-permutation/REXX/find-the-missing-permutation.rexx

@@ -0,0 +1,26 @@
+/*REXX program finds a  missing permuation  from an internal list.      */
+
+list='ABCD CABD ACDB DACB BCDA ACBD ADCB CDAB DABC BCAD CADB CDBA',
+     'CBAD ABDC ADBC BDCA DCBA BACD BADC BDAC CBDA DBCA DCAB'
+
+@.=;   @abcU='ABCDEFGUIJKLMNOPQRSTUVWXYZ'
+things=4
+bunch=4
+                 do j=1 for things     /*build list of permutation obj. */
+                 $.j=substr(@abcu,j,1)
+                 end   /*j*/
+call permset 1
+exit
+/*─────────────────────────────────────PERMSET subroutine───────────────*/
+permset:procedure expose $. @. bunch list things;   parse arg ?
+if ?>bunch then do;   _=@.1;         do m=2 to bunch
+                                     _=_||@.m
+                                     end   /*m*/
+                if wordpos(_,list)==0 then say _ ' is missing from the list.'
+                end
+           else do x=1 for things      /*construction a new permuation. */
+                  do k=1 for ?-1;  if @.k==$.x then iterate x;  end  /*k*/
+                @.?=$.x
+                call permset ?+1
+                end   /*x*/
+return