stack_linkedlist_optimal.c

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

#define EMPTY (-1)
#define INT_MIN (-2147483648)
#define STACK_EMPTY INT_MIN

typedef struct node{
    int value;
    struct node *next;
} node;


bool push(node **head, int value){
    node *newnode = malloc(sizeof(node));
    newnode->value = value;
    newnode->next = (*head);
    (*head) = newnode;
    return true;
}

int pop(node **head){
    if((*head) == NULL)
        return STACK_EMPTY;

    int result = (*head)->value;
    node *temp = (*head);
    (*head) = (*head)->next;
    free(temp);
    return result;
}

int main(){

    node *head1 = NULL;
    node *head2 = NULL;
    node *head3 = NULL;

    push(&head1, 56);
    push(&head1, 13);
    push(&head1, 12);

    push(&head2, 17);
    push(&head2, 19);
    push(&head2, 28);

    push(&head3, 26);
    push(&head3, 24);
    push(&head3, 32);

    int t;
    while((t=pop(&head2))!=STACK_EMPTY){
        printf("t = %d\n", t);
    }
    return 0;
}