PUSH and POP operations in Stack in C Program

PUSH and POP operations on stack using an array with C program

Two Basic Operations on Stack

PUSH
POP

Push and Pop operation in stack in C : Algorithm

PUSH(Stack, N, Item)

This algorithm will insert Item at top to Stack having size N. Here initial index for stack is 0.

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POP(Stack, N)

This algorithm will delete the top element from the Stack having size N. Here initial index for stack is 0.

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C program to implement push and pop operations on a stack using an array is as follows:

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#include<stdio.h>
#include<conio.h>

#define N 5
int top = -1;
int stack[N];

//Function prototypes
void push(int item);
int pop();

void main()
{
      int item, choice, cont = 1;
      clrscr();

while(cont == 1)
      {
            printf("\n1.Push onto stack.\n");
            printf("\n2.Pop from stack.\n");

printf("\nEnter your choice: ");
            scanf("%d",&choice);

switch(choice)
            {
                  case 1:
                        printf("\nEnter the value of item:");
                        scanf("%d",&item);
                        push(item);
                        break;
                  case 2:
                        item = pop();
                        if(item != NULL)
                        {
                            printf("\nItem popped out: %d\n",item);
                        }                       
                        break;
                  default:
                        printf("\nInvalid choice.\n");
                        break;
            }
            printf("\nDo you want to continue (1/0): ");
            scanf("%d",&cont);
      }
      getch();
}

//Function Definition for push operation
void push(int item)
{
      if(top >= N-1)
      {
            printf("\nStack Overflow. Push not possible.\n");
      }
      else
      {
            top = top+1;
            stack[top] = item;
      }
}

//Function for pop operation
int pop()
{
      int item = NULL;

if(top == -1)
      {
            printf("\nStack Underflow. Pop not possible.\n");
      }
      else
      {
            top = top-1;
            item = stack[top+1];
            stack[top+1]=NULL;
      }
      return(item);
}

Output :

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1.Push onto stack.
2.Pop from stack.
Enter your choice: 1
Enter the value of item:10
Do you want to continue (1/0): 1

1.Push onto stack.
2.Pop from stack.
Enter your choice: 1
Enter the value of item:20
Do you want to continue (1/0): 1

1.Push onto stack.
2.Pop from stack.
Enter your choice: 11
Enter the value of item:30
Do you want to continue (1/0): 1

1.Push onto stack.
2.Pop from stack.
Enter your choice: 2
Item popped out: 30
Do you want to continue (1/0): 1

1.Push onto stack.
2.Pop from stack.
Enter your choice: 1
Enter the value of item:40
Do you want to continue (1/0): 1

1.Push onto stack.
2.Pop from stack.
Enter your choice: 1
Enter the value of item:50
Do you want to continue (1/0): 1

1.Push onto stack.
2.Pop from stack.
Enter your choice: 1
Enter the value of item:60
Do you want to continue (1/0): 1

1.Push onto stack.
2.Pop from stack.
Enter your choice: 1
Enter the value of item:70
Stack Overflow. Push not possible.
Do you want to continue (1/0): 1

1.Push onto stack.
2.Pop from stack.
Enter your choice: 2
Item popped out: 60
Do you want to continue (1/0):0

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