A stack is an abstract data structure that contains a collection of elements.
What is a stack?
Stack is known as LIFO(Last in First Out) functionality which means a thing or an object which has been added last time will out first. Like Placing books on one an other the last book we placed will be picked first to collect all books.
Some of the principle operations in the stack are −
Push – This adds a data value to the top of the stack.
Pop – This removes the data value on top of the stack
Peek – This returns the top data value of the stack
C++ Program to Implement Stack Using Array
#include<iostream>
#include<conio.h>
#include<stdlib.h>
#include<stdio.h>
using namespace std;
int top=-1; // -1 shows that stack is not created
int size=0; // initial size is zero
int *stk; // initialization of dynamic array of typ int [works as stack]
/////////////////////////////////////////////////////////////////////////////////////
void createstk();
void menu();
void display();
void deletestk();
void clearstk(); // declaration of functions
int pop();
void push(int);
void findelement();
int isfull();
int isempty();
int checkIndex=0;
void find_by_position();
/////////////////////////////////////////////////////////////////////////////////////
void menu()
{
int option;
system(“pause”);
system(“cls”);
while(option<1||option>10) // continue till we select option from 1-10
{
system(“cls”);
cout<<“press 0 to find element by position\n”;
cout<<“press 1 to create stack\n”;
cout<<“press 2 to display stack\n”;
cout<<“press 3 to clear stack\n”;
cout<<“press 4 to delete stack\n”;
cout<<“press 5 to find element in stack\n”;
cout<<“press 6 to remove element from stack\n” ;
cout<<“press 7 to add element in stack\n”;
cout<<“press 8 to check whether stack is full\n”;
cout<<“press 9 to check whether stack is empty\n”;
cout<<“press 10 to exit\n”;
cin>>option;
switch(option)
{
case 0:
find_by_position();
break;
case 1:
createstk();
break;
case 2:
display();
break;
case 3:
clearstk();
break;
case 4:
deletestk();
break;
case 5:
findelement();
break;
case 6:
{
if(top<0)
cout<<“stack not created\n”; // check to see if stack is created or not
if(isempty()==1)
cout<<“stack is empty\n”; // check to see if stack is empty
else
pop(); // pop element
}
menu();
break;
case 7:
{
int a;
if(top<0)
cout<<“stack not created\n”; // check to see if stack is created or not
else
if(isfull()==1 )
cout<<“stack is full\n”; //check to see if stack is full
else
cout<<“enter element to push on stack:”; // take element to push on stack if it is not full
cin>>a;
push(a);
}
menu();
break;
case 8:
{
int a;
if(top<0) //check to see if stack is created or not
cout<<“stack not created\n”;
else
isfull(); //calling isfull funtion
if(a==1)
cout<<“stack is full\n”; //if isfull function returns 1 (true) then stack is full
else
cout<<“stack is not full\n”; //else stack is not full
}
menu();
break;
case 9:
{
int a;
if(top<0)
cout<<“stack not created\n”; //check to see if stack is created or not
else
isempty(); //calling isempty function
if(a==1) //if isempty function returns 1(true) then stack is empty
cout<<“stack is empty\n”;
else
cout<<“stack is not empty\n”; //else stack is not empty
}
menu();
break;
case 10:
exit(0); //calling default built in function to exit program
break;
default:
cout<<“invalid option”;
break;
}
}
}
///////////////////////////////////////////////////////////////////////////////////////////
void createstk()
{
cout<<“enter total size of stack:”;
cin>>size;
stk=new int[size]; // take total size of stack
do
{
cout<<“how many elements do you want to enter?\n”; //take current size of stack that we are going to use yet
cin>>top;
}
while(top<1||top>size); //prompt to enter current size till size entered is less then 1
// or greater then total size
cout<<“enter elements\n”;
for(int i=0;i<top;i++) //for loop from index 0 to current size (top)
{
cin>>stk[i]; //input value in stack
}
menu(); //function call to enter main menu again
}
///////////////////////////////////////////////////////////////////////////////////////////
void display()
{
if(top<0)
cout<<“stack not created\n”; //check to see if stack is created
else
cout<<“total number of elements in stack are :”<<top; //displays total number of elements in stack
//by diplaying current value of top
cout<<“\nand are as follows\n”;
for(int i=0;i<top;i++) //loop from 0 index to top
cout<<stk[i]<<endl; //displays value in stack
getch();
menu(); //function call to enter main menu again
}
////////////////////////////////////////////////////////////////////////////////////////////
void clearstk()
{
if(top<0)
cout<<“stack not created\n”; //check to see if stack is created or not
else
top=0; //if stack is created then make top=0 and clear it
cout<<“stack is cleared\n”;
menu();
}
////////////////////////////////////////////////////////////////////////////////////////////////
void deletestk()
{
if(top<0)
cout<<“stack not created\n”; //check to see if stack is created or not
else
top=-1;
cout<<“stack is deleted\n”; //if stack is created then make top=-1 and delete it
menu();
}
///////////////////////////////////////////////////////////////////////////////////////////////
void findelement()
{
int item,temp=0; //initialize temp variable from 0 + intializing variable to enter item
//to be found + intitailaizing counter variable ‘i’
if(top<0)
cout<<“stack not created\n”; //check to see if stack is created or not
else
{
cout<<“enter item you want to find\n”;
cin>>item; //input item to be found in stack
for(int m=0;m<top;m++) //loop starts from zero index and continue upto top
{
if(stk[m]==item) //compare each content of stack with value entere
{
cout<<“item found at “<<m<<endl;
temp=1;
}
//if item found then change value of temp to false the condition
}
//control comes out of loop
if(temp==0)
{
cout<<“item not found\n”; //if temp!=1 displays that item not found
}
}
menu();
}
/////////////////////////////////////////////////////////////////////////////////////////
void push(int i) //take arguement
{
stk[top]=i; //places arguement at top
top++; //increment top to show next available position
}
////////////////////////////////////////////////////////////////////////////////////////
int pop()
{
int i=stk[top]; //remove element from top
top–; //decrements top
return i;
}
///////////////////////////////////////////////////////////////////////////////////
int isfull()
{
if( top==size) //check if top is equal to total size
return 1 ; //return true i-e stack is full
else
return 0; //else return false tnat stack is not full
}
/////////////////////////////////////////////////////////////////////////////////
int isempty()
{
if(top==0) //check if top is zero
return 1; //return true that stack is empty
else
return 0; //else return false that stack is not empty
}
/////////////////////////////////////////////////////////////////////////////////////////
void find_by_position()
{
int pos;
if(top<0)
cout<<“stack not created\n”;
else
if(top==0)
cout<<“stack is empty\n”;
else
{
do
{
cout<<“enter position to find its content\n”;
cin>>pos;
}while(pos<0||pos>size);
for(int i=0;i<size;i++)
{
if(i==pos)
{
cout<<“item at position “<<i<<” is “<<stk[i]<<endl;
} //if closed
} //for closed
} //else closed
menu();
} //function closed
int main()
{
cout<<“welcome to stack application\n”;
menu(); //funtion call to main menu
getch();
}