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qsort_c.f90
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qsort_c.f90
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! Recursive Fortran 95 quicksort routine
! sorts real numbers into ascending numerical order
! Author: Juli Rew, SCD Consulting ([email protected]), 9/03
! Based on algorithm from Cormen et al., Introduction to Algorithms,
! 1997 printing
! Made F conformant by Walt Brainerd
! Smaller adjustments for personal usage by Nikola Mirkov
module qsort_c_module
implicit none
public :: QsortC
private :: Partition
contains
recursive subroutine QsortC(A)
real, intent(in out), dimension(:) :: A
integer :: iq
if(size(A) > 1) then
call Partition(A, iq)
call QsortC(A(:iq-1))
call QsortC(A(iq:))
endif
end subroutine QsortC
subroutine Partition(A, marker)
real, intent(in out), dimension(:) :: A
integer, intent(out) :: marker
integer :: i, j
real :: temp
real :: x ! pivot point
x = A(1)
i= 0
j= size(A) + 1
do
j = j-1
do
if (A(j) <= x) exit
j = j-1
end do
i = i+1
do
if (A(i) >= x) exit
i = i+1
end do
if (i < j) then
! exchange A(i) and A(j)
temp = A(i)
A(i) = A(j)
A(j) = temp
elseif (i == j) then
marker = i+1
return
else
marker = i
return
endif
end do
end subroutine Partition
recursive subroutine QsortCInt(A)
integer, intent(in out), dimension(:) :: A
integer :: iq
if(size(A) > 1) then
call PartitionInt(A, iq)
call QsortCInt(A(:iq-1))
call QsortCInt(A(iq:))
endif
end subroutine QsortCInt
subroutine PartitionInt(A, marker)
integer, intent(in out), dimension(:) :: A
integer, intent(out) :: marker
integer :: i, j
! integer :: temp
integer :: x ! pivot point
x = A(1)
i= 0
j= size(A) + 1
do
j = j-1
do
if (A(j) <= x) exit
j = j-1
end do
i = i+1
do
if (A(i) >= x) exit
i = i+1
end do
if (i < j) then
! exchange A(i) and A(j)
! temp = A(i)
! A(i) = A(j)
! A(j) = temp
call swapInt( A(i), A(j) )
elseif (i == j) then
marker = i+1
return
else
marker = i
return
endif
end do
end subroutine PartitionInt
recursive subroutine QsortCIndx(A,ind)
real, intent(in out), dimension(:) :: A
integer, intent(in out), dimension(:) :: ind
integer :: iq
if(size(A) > 1) then
call PartitionIndx(A, ind, iq)
call QsortCIndx(A(:iq-1), ind(:iq-1))
call QsortCIndx(A(iq:), ind(iq:))
endif
end subroutine QsortCIndx
subroutine PartitionIndx(A, ind, marker)
real, intent(in out), dimension(:) :: A
integer, intent(in out), dimension(:) :: ind
integer, intent(out) :: marker
integer :: i, j
real :: temp
real :: x ! pivot point
x = A(1)
i= 0
j= size(A) + 1
do
j = j-1
do
if (A(j) <= x) exit
j = j-1
end do
i = i+1
do
if (A(i) >= x) exit
i = i+1
end do
if (i < j) then
! exchange A(i) and A(j)
temp = A(i)
A(i) = A(j)
A(j) = temp
call swapInt( ind(i), ind(j) )
elseif (i == j) then
marker = i+1
return
else
marker = i
return
endif
end do
end subroutine PartitionIndx
subroutine swap(a,b)
real, intent(inout) :: a,b
real :: temp
temp = a
a = b
b = temp
end subroutine swap
subroutine swapInt(a,b)
integer, intent(inout) :: a,b
integer :: temp
temp = a
a = b
b = temp
end subroutine swapInt
end module qsort_c_module