Data commit

Task/Permutations/ABAP/permutations.abap

@@ -0,0 +1,100 @@
+data: lv_flag type c,
+      lv_number type i,
+      lt_numbers type table of i.
+
+append 1 to lt_numbers.
+append 2 to lt_numbers.
+append 3 to lt_numbers.
+
+do.
+  perform permute using lt_numbers changing lv_flag.
+  if lv_flag = 'X'.
+    exit.
+  endif.
+  loop at lt_numbers into lv_number.
+    write (1) lv_number no-gap left-justified.
+    if sy-tabix <> '3'.
+      write ', '.
+    endif.
+  endloop.
+  skip.
+enddo.
+
+" Permutation function - this is used to permute:
+" Can be used for an unbounded size set.
+form permute using iv_set like lt_numbers
+             changing ev_last type c.
+  data: lv_len     type i,
+        lv_first   type i,
+        lv_third   type i,
+        lv_count   type i,
+        lv_temp    type i,
+        lv_temp_2  type i,
+        lv_second  type i,
+        lv_changed type c,
+        lv_perm    type i.
+  describe table iv_set lines lv_len.
+
+  lv_perm = lv_len - 1.
+  lv_changed = ' '.
+  " Loop backwards through the table, attempting to find elements which
+  " can be permuted. If we find one, break out of the table and set the
+  " flag indicating a switch.
+  do.
+    if lv_perm <= 0.
+      exit.
+    endif.
+    " Read the elements.
+    read table iv_set index lv_perm into lv_first.
+    add 1 to lv_perm.
+    read table iv_set index lv_perm into lv_second.
+    subtract 1 from lv_perm.
+    if lv_first < lv_second.
+      lv_changed = 'X'.
+      exit.
+    endif.
+    subtract 1 from lv_perm.
+  enddo.
+
+  " Last permutation.
+  if lv_changed <> 'X'.
+    ev_last = 'X'.
+    exit.
+  endif.
+
+  " Swap tail decresing to get a tail increasing.
+  lv_count = lv_perm + 1.
+  do.
+    lv_first = lv_len + lv_perm - lv_count + 1.
+    if lv_count >= lv_first.
+      exit.
+    endif.
+
+    read table iv_set index lv_count into lv_temp.
+    read table iv_set index lv_first into lv_temp_2.
+    modify iv_set index lv_count from lv_temp_2.
+    modify iv_set index lv_first from lv_temp.
+    add 1 to lv_count.
+  enddo.
+
+  lv_count = lv_len - 1.
+  do.
+    if lv_count <= lv_perm.
+      exit.
+    endif.
+
+    read table iv_set index lv_count into lv_first.
+    read table iv_set index lv_perm into lv_second.
+    read table iv_set index lv_len into lv_third.
+    if ( lv_first < lv_third ) and ( lv_first > lv_second ).
+      lv_len = lv_count.
+    endif.
+
+    subtract 1 from lv_count.
+  enddo.
+
+  read table iv_set index lv_perm into lv_temp.
+  read table iv_set index lv_len into lv_temp_2.
+  modify iv_set index lv_perm from lv_temp_2.
+  modify iv_set index lv_len from lv_temp.
+endform.