挿入ソート

少し改良。配列のサイクリックシフトで。

module m_isort2
    implicit none
    contains
        
    subroutine isort2y( x )
      real, intent(in out) :: x(:)
      integer :: j, k, n
      n = size(x)
      if (n <= 1) return
      do k = n - 1, 1, -1
        do j = k + 1, n
          if ( x(k) < x(j) ) exit 
        end do
        x(k:j - 1) = cshift( x(k:j - 1), 1 )
      end do
      return
    end subroutine isort2y
  
  end module

  program sort2
    use m_isort2
    implicit none
    real, allocatable :: x(:)
    integer :: i 
    !
    allocate( x(10**5) )
    call random_seed()
    call random_number(x)
    call isort2y(x)
    print *, x
    do i = 1, size(x) - 1 ! check
      if (x(i) > x(i + 1) ) print *, 'error!', i
    end do
    stop
  end program sort2