If we insert any node at first position and delete from first in singly linked list, it becomes stack
Function: PUSH(X, FIRST)
- Given X, a new element, this function inserts a new node at the first position of linked list.
- FIRST is a pointer to the first element of a linked linear list.
- Typical node contains INFO and LINK fields.
- AVAIL is a pointer to the top element of the availability stack.
- NEW is a temporary pointer variable.
- This function returns address of FIRST node
1. [Underflow?]
If AVAIL = NULL
Then Write (“Availability Stack Underflow”)
Return(FIRST)
2. [Obtain address of next free Node]
NEW<--AVAIL
3. [Remove free node from Availability Stack]
AVAIL<--LINK(AVAIL)
4. [Initialize fields of new node and its link to the list]
INFO (NEW) <-- X
LINK (NEW) <-- FIRST
5 [Return address of new node]
Return (NEW)
When INSERT is invoked it returns a pointer value to the variable FIRST
FIRST <-- INSERT (X, FIRST)
Function: POP( FIRST)
- This algorithm deletes and returns First Node from Singly Linked List.
- FIRST is a pointer to the first element of a linked linear list.
- Typical node contains INFO and LINK fields.
1. [Is Empty list?]
If FIRST = NULL
Then write (‘Underflow’)
Return(0)
2. [Delete First Node]
VALUE <-- INFO (FIRST)
SAVE <-- FIRST
FIRST <-- LINK (FIRST)
3. [Free Deleted Node]
FREE (SAVE)
Return (VALUE)
