STACK.c

#include <stdio.h>
#include <stdlib.h>
int s[5],top=-1;

void push()
{
    if(top==4)
        printf("\nStack overflow!!!!");
    else
    {
        printf("\nEnter element to insert:");
        scanf("%d",&s[++top]);
    }
}

void pop()
{
    if(top==-1)
        printf("\nStack underflow!!!");
    else
        printf("\nElement popped is: %d",s[top--]);
}
void disp()
{
    int t=top;
    if(t==-1)
        printf("\nStack empty!!");
    else
        printf("\nStack elements are:\n");
    while(t>=0)
        printf("%d ",s[t--]);
}
void pali()
{
    int num[5],rev[5],i,t;
    for(i=0,t=top;t>=0;i++,t--)
        num[i]=rev[t]=s[t];
    for(i=0;i<=top;i++)
        if(num[i]!=rev[i])
        break;
    /*printf(" num     rev\n");
    for(t=0;t<=top;t++)
      printf("%4d   %4d\n",num[t],rev[t]);*///remove /* */ to display num and rev
    if(i==top+1)
        printf("\nIt is a palindrome");
    else
        printf("\nIt is not a palindrome");
}

int main()
{
    int ch;
    do
    {
        printf("\n...Stack operations.....\n");
        printf("1.PUSH\n");
        printf("2.POP\n");
        printf("3.Palindrome\n");
        printf("4.Display\n");
        printf("5.Exit\n________________\n");
        printf("Enter choice:");
        scanf("%d",&ch);
        switch(ch)
        {
            case 1:push();break;
            case 2:pop();break;
            case 3:pali();break;
            case 4:disp();break;
            case 5:exit(0);
            default:printf("\nInvalid choice");
        }
    }
    while(1);
    return 0;
}