linkedliststack.c

#include<stdio.h>
#include<stdlib.h>

//push isEmpty pop peek

typedef struct Node{
    int data;
    struct Node *next;
} Node;

Node *top = NULL;

void push(int data){
    Node *newnode = malloc(sizeof(Node));

    if(newnode == NULL){
        printf("error maximum heap size reached");
        return;
    }

    newnode->data = data;
    newnode->next = top;
    top = newnode;
}

int isEmpty(){
    if(top == NULL){
        printf("Empty stack");
        return 1;
    } else {
        return 0;
    }
}

int pop(){

    if(isEmpty()){
        return -1;
    }
    
    int val = top->data;
    Node *temp = top;
    top = top->next;
    free(temp);
    return val;

}

int peek(){
    if(isEmpty()){
        return -1;
    }

    return top->data;
}

int main(){
    // 1. Add some data
    push(10);
    push(20);
    push(30);

    // 2. See what's at the top
    printf("Top element is: %d\n", peek());

    // 3. Remove and print everything
    printf("Popping elements:\n");
    while (top != NULL) {
        printf("%d ", pop());
    }
    
    // 4. Test the empty case
    pop(); 

    return 0;

}