#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "Stack.h"

struct node {
    int item;
    struct node *next;
};

struct stack {
    struct node *top;
};

static struct node *newNode(int item) {
    struct node *n = malloc(sizeof(struct node));
    n->item = item;
    n->next = NULL;
    return n;
}

Stack StackNew(void) {
    Stack s = malloc(sizeof(struct stack));
    s->top = NULL;
    return s;
}

void StackFree(Stack s) {
    if (s == NULL) {
        return;
    }
    struct node *curr = s->top;
    while (curr != NULL) {
        struct node *temp = curr;
        curr = curr->next;
        free(temp);
    }
    free(s);
}

void StackPush(Stack s, int item) {
    struct node *n = newNode(item);
    n->next = s->top;
    s->top = n;
}

int StackPop(Stack s) {
    struct node *temp = s->top;
    int item = temp->item;

    s->top = temp->next;
    free(temp);

    return item;
}