STACK implementation (STRUCTURE & POINTER)

 By: Himanshu Tiwari

#include<stdio.h>

#include<stdlib.h>

int x,choice;

struct stack{

int size;

int top;

int  *arr;

};

void push(struct stack *ptr,int size){

    if(ptr->top>=size-1){

        printf("STACK OVERFLOW \n");

    }else{

        printf("Enter number to be PUSH : ");

        scanf("%d",&x);

        ptr->top++;

        ptr->arr[ptr->top]=x;

        printf("Pushed successfully !\n");

    }

}

void display(struct stack *ptr){

if(ptr->top==-1){

    printf("STACk is empty \n");

}

for(int i=ptr->top; i>=0; i--){

    printf("%d\n",ptr->arr[i]);

}

}

void pop(struct stack *ptr){

    if(ptr->top==-1){

        printf("STACK UNDERFLOW \n");

    }else{

        printf("popped element : %d\n",ptr->arr[ptr->top]);

        ptr->top--;

    }

}

int main(){

struct stack *sp=(struct stack *)malloc(sizeof(struct stack));

printf("Enter the size of STACK : ");

scanf("%d",&sp->size);

sp->top=-1;

sp->arr=(int *)malloc(sp->size*sizeof(int));

//stack has been created

printf("\n\t 1.PUSH\n\t 2.POP\n\t 3.DISPLAY\n\t 4.EXIT\n");

do{

    printf("enter the choice : ");

    scanf("%d",&choice);

    switch(choice){

        case 1 : push(sp,sp->size);

        break;

        case 2 :pop(sp);

        break;

        case 3 : display(sp);

        break;

        case 4 : printf("EXIT POINT\n");

        break;

        default : printf("entered wrong choice !\n");

        break;

    }

}while(choice!=4);

return 0;

}