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Doubly-linked list/Traversal: Difference between revisions
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PL/I code moved to its correct alphabetical position.
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: (2printReversed *DL) # Print it in reversed order
B C A</pre>
=={{header|PL/I}}==
<lang PL/I>/* To implement a doubly-linked list -- i.e., a 2-way linked list. */
doubly_linked_list: proc options (main);
define structure
1 node,
2 value fixed,
2 fwd_pointer handle(node),
2 back_pointer handle(node);
declare (head, tail, t) handle (node);
declare null builtin;
declare i fixed binary;
head, tail = bind(:node, null:);
do i = 1 to 10; /* Add ten items to the tail of the queue. */
if head = bind(:node, null:) then
do;
head,tail = new(:node:);
get list (head => value);
put skip list (head => value);
head => back_pointer,
head => fwd_pointer = bind(:node, null:); /* A NULL link */
end;
else
do;
t = new(:node:);
t => back_pointer = tail; /* Point the new tail back to the old */
/* tail. */
tail => fwd_pointer = t; /* Point the tail to the new node. */
t => back_pointer = tail; /* Point the new tail back to the old */
/* tail. */
tail = t; /* Point at teh new tail. */
tail => fwd_pointer = bind(:node, null:);
/* Set the tail link to NULL */
get list (tail => value) copy;
put skip list (tail => value);
end;
end;
if head = bind(:node, null:) then return; /* Empty list. */
/* Traverse the list from the head. */
put skip list ('In a forwards direction, the list has:');
t = head;
do while (t ^= bind(:node, null:));
put skip list (t => value);
t = t => fwd_pointer;
end;
/* Traverse the list from the tail to the head. */
put skip list ('In the reverse direction, the list has:');
t = tail;
do while (t ^= bind(:node, null:));
put skip list (t => value);
t = t => back_pointer;
end;
end doubly_linked_list;</lang>
Output:
<pre>
In a forwards direction, the list has:
1
2
3
4
5
16
7
8
9
10
In the reverse direction, the list has:
10
9
8
7
16
5
4
3
2
1</pre>
=={{header|PureBasic}}==
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