Doubly-linked list/Definition: Difference between revisions
added Unicon example
(added Unicon example) |
|||
Line 1,171:
n1 = firstNode x
Just n2 = nextNode x n1</lang>
==Icon and {{header|Unicon}}==
Uses Unicon's classes.
The DoubleList is made from elements of DoubleLink. [[Doubly-Linked List (element)#Icon_and_Unicon]], [[Doubly-Linked List (element insertion)#Icon_and_Unicon]] and [[Doubly-Linked List (traversal)#Icon_and_Unicon]]
<lang Unicon>
class DoubleList (item)
method head ()
node := item
every (node := node.traverse_backwards ()) # move to start of list
return node
end
method tail ()
node := item
every (node := node.traverse_forwards ()) # move to end of list
return node
end
method insert_at_head (value)
head().insert_before (DoubleLink(value))
end
method insert_at_tail (value)
tail().insert_after (DoubleLink (value))
end
# insert a node for new_value after that for target_value,
# i.e. in the middle of the list
method insert_after (target_value, new_value)
node := head ()
every node := head().traverse_forwards () do
if (node.value = target_value)
then {
node.insert_after (DoubleLink (new_value))
break
}
end
# constructor initiates a list making a node from given value
initially (value)
self.item := DoubleLink (value)
end
</lang>
An <code>insert_before</code> method was added to the DoubleLink class:
<lang Unicon>
# insert given node before this one, losing its existing connections
method insert_before (node)
if (\prev_link) then prev_link.next_link := node
node.prev_link := prev_link
node.next_link := self
self.prev_link := node
end
</lang>
To test the double-linked list:
<lang Unicon>
procedure main ()
dlist := DoubleList (5)
every i := 4 to 1 by -1 do
dlist.insert_at_head (i)
every i := 6 to 10 do
dlist.insert_at_tail (i)
dlist.insert_after (3, 11)
every node := dlist.head().traverse_forwards () do
write (node.value)
end
</lang>
Output:
<pre>
1
2
3
11
4
5
6
7
8
9
10
</pre>
=={{header|J}}==
| |||