![8
Push Algorithm
begin procedure push: stack, data
if stack is full
return null
endif
top ← top + 1
stack[top] ← data
end procedure](https://image.slidesharecdn.com/4stack-210409033116/85/Algorithm-and-Data-Structure-Stack-8-320.jpg)
![Pop Algorithm
begin procedure pop: stack
if stack is empty
return null
endif
data ← stack[top]
top ← top - 1
return data
end procedure
11](https://image.slidesharecdn.com/4stack-210409033116/85/Algorithm-and-Data-Structure-Stack-11-320.jpg)
![Peek or Top
Peek or Top: Returns the element on top of the stack.
It takes O(1)O(1) time as finding the value stored at a
particular index in an array is a constant time
operation. The operation is to get the top data
element of the stack, without removing it
12
Peek Algorithm:
begin procedure peek
return stack[top]
end procedure](https://image.slidesharecdn.com/4stack-210409033116/85/Algorithm-and-Data-Structure-Stack-12-320.jpg)
Algorithm and Data Structure - Stack
- 1. Algorithm and Data Structure Andi Nurkholis, S.Kom, M.Kom Study Program of Informatics Faculty of Engineering and Computer Science SY. 2020-2021 April 12, 2021
- 2. 2 4 Stack
- 3. 3 What is Stack? Stack is a linear data structure which follows a particular order in which the operations are performed. The order may be LIFO (Last In First Out) or FILO (First In Last Out) In stacks, the insertion and deletion of elements happen only at one endpoint of it.
- 5. 5 Stack Operations 1) Push 2) Pop 3) Peek or Top 4) IsEmpty 5) IsFull
- 6. 6 Push Push: Adds an item in the stack. If the stack is full, then it is said to be an Overflow condition.
- 7. Steps of Push Step 1 − Checks if the stack is full. Step 2 − If the stack is full, produces an error and exit. Step 3 − If the stack is not full, increments top to point next empty space. Step 4 − Adds data element to the stack location, where top is pointing. Step 5 − Returns success. 7
- 8. 8 Push Algorithm begin procedure push: stack, data if stack is full return null endif top ← top + 1 stack[top] ← data end procedure
- 9. 9 Pop Pop: Removes an item from the stack. The items are popped in the reversed order in which they are pushed. If the stack is empty, then it is said to be an Underflow condition.
- 10. Steps of Pop Step 1 − Checks if the stack is empty. Step 2 − If the stack is empty, produces an error and exit. Step 3 − If the stack is not empty, accesses the data element at which top is pointing. Step 4 − Decreases the value of top by 1. Step 5 − Returns success. 10
- 11. Pop Algorithm begin procedure pop: stack if stack is empty return null endif data ← stack[top] top ← top - 1 return data end procedure 11
- 12. Peek or Top Peek or Top: Returns the element on top of the stack. It takes O(1)O(1) time as finding the value stored at a particular index in an array is a constant time operation. The operation is to get the top data element of the stack, without removing it 12 Peek Algorithm: begin procedure peek return stack[top] end procedure
- 13. IsEmpty IsEmpty: Checks whether the stack is empty. Returns true if stack is empty, else false. IsEmpty Algorithm: begin procedure isempty if top less than 1 return true else return false endif end procedure 13
- 14. IsFull IsEmpty: Checks whether the stack is full. Returns true if stack is full, else false. IsFull Algorithm: begin procedure isfull if top equals to MAXSIZE return true else return false endif end procedure 14
- 15. Working of Stack This abstract data type can be implemented in C in multiple ways. One such way is by using an array. Pro of using an array: No extra memory required to store the pointers. Con of using an array: The size of the stack is pre-set so it cannot increase or decrease. 15
- 16. Stack Application 1. Balancing of symbols 2. Infix to Postfix /Prefix conversion 3. Redo-undo features at many places like editors, photoshop. 4. Forward and backward feature in web browsers 5. Used in many algorithms like Tower of Hanoi, tree traversals, stock span problem, histogram problem. 16
- 17. Stack Application (Cont.) 6. Backtracking is one of the algorithm designing technique. 7. In Graph Algorithms like Topological Sorting and Strongly Connected Components 8. In Memory management any modern computer uses stack as the primary-management for a running purpose. 9. String reversal is also a another application of stack. 17
- 18. Thank You, Next … Queue April 12, 2021 Andi Nurkholis, S.Kom, M.Kom Study Program of Informatics Faculty of Engineering and Computer Science SY. 2020-2021