Data update

Task/Sorting-algorithms-Quicksort/Fortran/sorting-algorithms-quicksort.f

@@ -0,0 +1,57 @@
+       recursive subroutine fsort(a)
+      use inserts, only:insertion_sort !Not included in this posting
+      implicit none
+!
+! PARAMETER definitions
+!
+      integer, parameter  ::  changesize = 64
+!
+! Dummy arguments
+!
+      real, dimension(:) ,contiguous ::  a
+      intent (inout) a
+!
+! Local variables
+!
+      integer  ::  first = 1
+      integer  ::  i
+      integer  ::  j
+      integer  ::  last
+      logical  ::  stay
+      real  ::  t
+      real  ::  x
+!
+!*Code
+!
+      last = size(a, 1)
+      if( (last - first)<changesize )then
+          call insertion_sort(a(first:last))
+          return
+      end if
+      j = shiftr((first + last), 1) + 1
+                                     !
+      x = a(j)
+      i = first
+      j = last
+      stay = .true.
+      do while ( stay )
+          do while ( a(i)<x )
+              i = i + 1
+          end do
+          do while ( x<a(j) )
+              j = j - 1
+          end do
+          if( j<i )then
+              stay = .false.
+          else
+              t = a(i)      ! Swap the values
+              a(i) = a(j)
+              a(j) = t
+              i = i + 1     ! Adjust the pointers (PIVOT POINTS)
+              j = j - 1
+          end if
+      end do
+      if( first<i - 1 )call fsort(a(first:i - 1))   ! We still have some left to do on the lower
+      if( j + 1<last )call fsort(a(j + 1:last))     ! We still have some left to do on the upper
+      return
+      end subroutine fsort