Stack Data Structure: Overview, Implementation, Applications, and Operations, Essays (high school) of Computer science

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Data

Structure:

Stack

LECTURE 2

Stack Overview

 Stack ADT  Basic operations of stack  Pushing, popping etc.  Implementations of stacks using  array  linked list

The Stack ADT

 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).

 Fundamental operations:

 Push: Equivalent to an insert  Pop: Deletes the most recently inserted element  Top: Examines the most recently inserted element  Size: Number of elements a stack contains at present  Capacity: Number of elements it is capable of holding

Stack ADT

 Stacks are less flexible  but are more efficient and easy to implement  Stacks are known as LIFO (Last In, First Out) lists or or FILO(First In Last Out)The last element inserted will be the first to be retrieved.

Implementation:

There are two ways to implement

a stack:

• Using array
• Using linked list.

Array Implementation

 Need to declare an array size ahead of time  Associated with each stack is TopOfStack  for an empty stack, set TopOfStack to -  Push  (1) Increment TopOfStack by 1.  (2) Set Stack[TopOfStack] = X  Pop  (1) Set return value to Stack[TopOfStack]  (2) Decrement TopOfStack by 1  These operations are performed in very fast constant time

Stack class

 class Stack

 {

 private int[] ele; // name of the array for stack

 private int top; // storage index

 private int max; // total capacity

 public Stack(int size)

 {

 ele = new int[size];//Maximum size of Stack

 top = -1;

 max = size;

 }

Stack class

 Attributes of Stack

 maxTop: the max size of stack  top: the index of the top element of stack  values: point to an array which stores elements of stack

 Operations of Stack

 IsEmpty: return true if stack is empty, return false otherwise  IsFull: return true if stack is full, return false otherwise  Top: return the element at the top of stack  Push: add an element to the top of stack  Pop: delete the element at the top of stack  DisplayStack: print all the data in the stack

Push Stack

 void Push(const double x);  Push an element onto the stack  If the stack is full, print the error information.  Note top always represents the index of the top element. After pushing an element, increment top.

 public void push(int item)  { if (top == max - 1)  { Console.WriteLine("Stack Overflow");  return; }  else  { ele[++top] = item; }  }

Printing all the elements

 void printstack()

 Print all the elements

 public void printStack()  {  if (top == -1)  { Console.WriteLine("Stack is Empty");  return; }  else  {for (int i = 0; i <= top; i++)  { Console.WriteLine("{0} pushed into stack", ele[i]); }  }  }

Using Stack

static main(void) {  Stack p = new Stack(5);  p.push(5);  p.push(6);  p.push(-3);  p.push(-8);  p.printStack();  p.size();  p.pop(); }

result

Implementation based on Linked List

 Now, we will create our stack class. We will define a pointer, top, and initialize it to null. So, our LinkedListStack class will be:

Push an Element Onto a Stack

Pop an Element From the Stack

Peek the Element From Stack

Link for further studies

Prefix to Infix Conversion

 https://www.geeksforgeeks.org/prefix-infix-

conversion/

Sorting array using stacks

 https://www.geeksforgeeks.org/sorting-array-using-stacks/

Iterative tower of Hanoi

 https://www.geeksforgeeks.org/iterative-tower-of-hanoi/

How to create mergable stack?

 https://www.geeksforgeeks.org/create-mergable-stack/

Expression Evaluation

 https://www.geeksforgeeks.org/expression-evaluation/

The Celebrity Problem

 https://www.geeksforgeeks.org/the-celebrity-problem/