Linked Stack and Queue in Data Structure

Stack and Queue as Linked List

Linked Stack:

Algorithm: PUSH (TOP, INFO, LINK, TEMP, ITEM)

This procedure adds new node TEMP to the stack.

Step 1: Allocate memory for new node TEMP.

Step 2: [ Store the ITEM into INFO part of new node ]

TEMP  →  INFO := ITEM

Step 3: [ Make the TEMP node points to TOP. ]

TEMP  →  LINK := TOP

Step 4: [ Reset TOP pointer. ]

TOP := TEMP.

Step 5: [ Exit ]

Return.

Algorithm: POP (TOP, INFO, LINK, TEMP, ITEM)

This procedure deletes TOP node from STACK and store the data of INFO part into ITEM variable.

Step 1: [Check whether STACK is empty or not. ]

If TOP = NULL then

Write (‘Underflow! Stack is empty’)

and return.

[ End of If structure ]

Step 2: [ Store the data of TOP node into ITEM. ]

ITEM := TOP  →  INFO

Step 5: [ Remove the TOP node ]

TEMP := TOP

TOP := TOP  →   LINK

Step 6: Free the TEMP node.

Step 7: [ Exit ]

Return.

Linked Queue:

Algorithm: ADD (INFO, LINK, FRONT, REAR, TEMP, ITEM)

This procedure adds new node TEMP to the QUEUE.

Step 1: Allocate memory for new node TEMP.

Step 2: [ Store the ITEM into INFO part of new node ]

TEMP  →  INFO := ITEM

Step 3: [ Make the TEMP node points to NULL. ]

TEMP  →  LINK := NULL

Step 4: [ Add the ]

Front:= TEMP.

Step 5: [ Exit ]

Return.

Algorithm: POP (TOP, INFO, LINK, TEMP, ITEM)

This procedure deletes TOP node from STACK and store the data of INFO part into ITEM variable.

Step 1: [Check whether STACK is empty or not. ]

If TOP = NULL then

Write (‘Underflow! Stack is empty’) and return. [ End of If structure ]

Step 2: [ Store the data of TOP node into ITEM. ]

ITEM := TOP  →  INFO

Step 5: [ Remove the TOP node ]

TEMP := TOP

TOP := TOP  →   LINK

Step 6: Free the TEMP node.

Step 7: [ Exit ]

Return