Fortran 快速排序算法
快速排序（Quicksort）是对冒泡排序的一种改进。此段代码实现了Fortran快速排序算法。 Visual Fortran 提供的 QSort 函数内部即采用此算法。! Recursive Fortran 95 quicksort routine
! sorts real numbers into ascending numerical order
! Author: Juli Rew, SCD Consulting (juliana@ucar.edu), 9/03
! Based on algorithm from Cormen et al., Introduction to Algorithms,
! 1997 printing
! Made F conformant by Walt Brainerd
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
end module qsort_c_module
program www_fcode_cn
use qsort_c_module
implicit none
integer, parameter :: r = 10
real, dimension(1:r) :: myarray = (/0, 50, 20, 25, 90, 10, 5, 1, 99, 75/)
print *, "原数组:", myarray
call QsortC(myarray)
print *, "排序后:", myarray
end program www_fcode_cn
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