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

typedef struct Node node;
struct Node {
  int id;
  struct Node *next;
};

int peek(node *stack) { return stack->id; }

void push(node **stack, int id) {
  node *new = malloc(sizeof(node));
  new->id = id;

  new->next = *stack;
  *stack = new;
}

int pop(node **stack) {
  int id = (*stack)->id;
  node *next = (*stack)->next;
  free(*stack);
  *stack = next;
  return id;
}

void traverse(node *stack) {
  while (stack != NULL) {
    printf("%d ", stack->id);
    stack = stack->next;
  }
  printf("\n");
}

int main() {
  node *stack = NULL;
  push(&stack, 4);
  push(&stack, 99);
  push(&stack, 23);
  printf("Pop: %d\n", pop(&stack));
  printf("Traverseal: ");
  traverse(stack);

  // free
  while (stack != NULL)
    pop(&stack);
}