1. Data Structures & Algorithms
CHAPTER 6
Stacks
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2. Stacks and Queues Define two new abstract data types
*Both are restricted lists
*Can be implemented using arrays or linked lists
Stacks
“Last In First Out” (LIFO)
The last element inserted will be the first to be retrieved
Queues
“First In First Out” (FIFO)
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3. Stack Overview Stack ADT Basic operations of stack
*Pushing, popping etc.
Implementations of stacks using
*array
*linked list
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4. Stack ADT
A stack is a list of the same kind of elements with the restriction
that insertions and deletions can only be performed at the top of the list.
The other end is called bottom
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5. The Stack ADT
Stack applications can be classified into four broad categories:
reversing data,
pairing data,
postponing data usage
backtracking steps
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6. Conceptual Stacks
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7. Stacks
Stacks are also called Last Input First Output (LIFO) data structures.
Operations performed on stacks:
Push: Equivalent to insert
Pop: Deletes the most recently inserted element
Peek: Examines the most recently inserted element
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8. Stack Operations
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9. Push and Pop Primary operations: Push and Pop Push
Add an element to the top of the stack
B. Pop
Remove the element at the top of the stack
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10. Stacks implementation
Any list implementation can be used to implement a stack
Arrays (static: the size of stack is given initially)
Linked lists (dynamic: never become full)
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11. Implementation of Stacks as Arrays
The array implementing a stack is an array of reference variables
Each element of the stack can be assigned to an array slot
The top of the stack is the index of the last element added to the stack
To keep track of the top position, declare a variable called stackTop
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12. Implementation of Stacks as Arrays
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13. Constructors
Default constructor
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14. Initialize Stack
Method initializeStack:
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15. Empty Stack
Method isEmptyStack:
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16. Full Stack
Method isFullStack:
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17. Push
Method push:
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18. Peek
Method peek:
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19. Pop
Method pop:
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20. THE END
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