#include "stack.h"

bool InitStack(Stack * s) {
    *s = NULL;
    return true;
}

bool DestroyStack(Stack * s) {
    Stack p;

    while (*s) {
        p = *s;
        *s = (*s)->next;
        free (p);
    }
    return true;
}

bool Push(Stack * s, ElemType n) {
    Stack p = (stack *) malloc (sizeof(stack));
    if (!p) {
        fprintf(stderr,"No enough memory\n");
        return false;
    }
    p->data = n;
    p->next = *s;

    *s = p;

    return true;
}

bool Pop(Stack * s, ElemType * n) {
    if (!*s) {
        fprintf(stderr,"No element in stack!\n");
        return false;
    }
    *n = (*s)->data;
    Stack p = *s;
    *s = (*s)->next;
    free(p);

    return true;
}

ElemType GetTop(Stack * s) {
    if (*s)
        return (*s)->data;
    return -1;
}

bool StackIsEmpty (Stack * s) {
    if (!*s)
        return true;
    return false;
}