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Task/Sorting-algorithms-Permutation-sort/REXX/sorting-algorithms-permutation-sort.rexx

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+/*REXX program sorts an array using the  permutation-sort  method.      */
+call gen@                              /*generate the array elements.   */
+call show@ 'before sort'               /*show the before array elements.*/
+call permsets  items                   /*generate  items!  permutations.*/
+call permSort  items                   /*invoke the permutation sort.   */
+call show@ ' after sort'               /*show  after array elements*/
+say; say 'Permutation sort took' ? "permutations to find the sorted list."
+exit                                   /*stick a fork in it, we're done.*/
+/*──────────────────────────────────GEN@ subroutine─────────────────────*/
+gen@: @.=                              /*assign default value.          */
+@.1 = '---Four_horsemen_of_the_Apocalypse---'
+@.2 = '====================================='
+@.3 = 'Famine───black_horse'
+@.4 = 'Death───pale_horse'
+@.5 = 'Pestilence_[Slaughter]───red_horse'
+@.6 = 'Conquest_[War]───white_horse'
+list=                                  /*[↓] find # of entries in array.*/
+       do items=1  while @.items\=='';  @@.items=@.items;  end   /*items*/
+items=items-1                          /*adjust items slightly.         */
+return
+/*──────────────────────────────────INORDER subroutine──────────────────*/
+inOrder: parse arg q                   /*see if list  Q  is in order.   */
+_=word(q,1);  do j=2  to words(q);     x=word(q,j)
+              if x<_  then return 0    /*Out of order?  Then not sorted.*/
+              _=x
+              end   /*j*/
+  do k=1  for items; _=word(#.?,k); @.k=@@._; end  /*k*/    /*here it is*/
+return 1                               /*they're all in order finally.  */
+/*──────────────────────────────────PERMSETS subroutine─────────────────*/
+permsets: procedure expose !. # #.;    parse arg n,#.; #=0
+  do f=1  for n;  !.f=f;  end  /*f*/;  call .permAdd /*populate 1st perm*/
+  do while .permNext(n,0);             call .permAdd;  end   /*while ···*/
+return #
+.permNext:  procedure expose !.;    parse arg n,i;    nm=n-1
+  do k=nm  by -1  for nm;   kp=k+1
+  if !.k<!.kp   then  do;   i=k;   leave;   end
+  end   /*k*/
+      do j=i+1  while j<n;  parse value !.j !.n with !.n !.j;  n=n-1;  end
+if i==0 then return 0;              do j=i+1  while !.j<!.i;   end   /*j*/
+parse  value    !.j  !.i    with    !.i  !.j
+return 1
+.permAdd: #=#+1;     do j=1  for N;  #.#=#.# !.j;  end  /*j*/;       return
+/*──────────────────────────────────PERMSORT subroutine─────────────────*/
+permSort: do ?=1  until inOrder(aList) /*look for the sorted permutation*/
+aList=;   do m=1  for items; _=word(#.?,m); aList=aList @._;  end  /*m*/
+          end   /*?*/
+return
+/*──────────────────────────────────SHOW@ subroutine────────────────────*/
+show@: widthH=length(items)            /*maximum width of any line.     */
+  do j=1 for items; say 'element' right(j,widthH) arg(1)":" @.j; end /*j*/
+say copies('─', 79)                    /*show a nice separator line.    */
+return