stack-linkedlist.c

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

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

void push(Node **head, int data);
int pop(Node **head);
int peak(Node *head);

int main() {
  Node *head = NULL;

  push(&head, 1);
  push(&head, 2);
  push(&head, 5);
  push(&head, 3);

  printf("Peak %d\n", peak(head));

  printf("%d\n", pop(&head));
  printf("%d\n", pop(&head));

  printf("Peak %d\n", peak(head));

  printf("%d\n", pop(&head));
  printf("%d\n", pop(&head));
  printf("%d\n", pop(&head));
  
  return 0;
}

void push(Node **head, int data) {
  Node *new = (Node*)malloc(sizeof(Node));
  new->data = data;
  new->next = *head;

  *head = new;
}

int pop(Node **head) {
  if (*head == NULL) return -1;

  Node *t = *head;
  int val = t->data;
  *head = t->next;
  free(t);

  return val;
}

int peak(Node *head) {
  if (head == NULL) return -1;

  return head->data;
}