Linked Structures

Traverse and Print

Walk from the head pointer to null, visiting each node exactly once without random indexing.

Algorithm

The replay labels nodes by value, such as node(20), and never exposes object identity or memory addresses. This Fortran DSA implementation uses the same small chain as the rest of the DSA track.

Basic Implementation

basic.f90 
program linked_list_lesson
    implicit none
    type :: list_node
        integer :: value
        type(list_node), pointer :: next => null()
    end type list_node
    type(list_node), pointer :: head, cursor, new_head
    type(list_node), pointer :: n1, n2, n3, n4

    allocate(n1); n1%value = 10
    allocate(n2); n2%value = 20
    allocate(n3); n3%value = 30
    n1%next => n2; n2%next => n3; n3%next => null()
    head => n1
    call print_chain(head)
contains
    subroutine print_chain(start)
        type(list_node), pointer :: start
        type(list_node), pointer :: cur
        cur => start
        do while (associated(cur))
            write(*, '(I0,A)', advance='no') cur%value, ' -> '
            cur => cur%next
        end do
        write(*, '(A)') 'null'
    end subroutine print_chain
end program linked_list_lesson

Complexity

  • Time: O(n)
  • Space: O(1)

Implementation notes

  • Keep the explicit node and pointer/reference operations; array shortcuts hide the linked-list state this lesson is meant to replay.
  • The final output prints the chain in a deterministic a -> b -> null form for cross-language comparison.
cursor A cursor reference names the node currently being visited.
null stop Traversal ends when the cursor reaches the null marker.