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

struct _Cvor;
typedef struct _Cvor * Position;

struct _Cvor
{
    int Element;
    Position Next;
};

int GetValueFromRange(int, int);
int Push(Position, int, int);
int Pop(Position, int);
void PrintList(Position, int);

void main(void)
{
    struct _Cvor S;
    char izbor = 0;
    int n = 0;
    int max = 0;

    S.Next = NULL;
    S.Element = -1;

    while(max < 5)
    {
        printf("\r\nUnesite velicinu stoga <5-20> : ");
        scanf_s(" %d", &max);
        if(max < 5 || max > 20)
        {
            max = 0;
            printf("\r\nPogresan unos!");
        }
    }

    S.Next = NULL;
    srand((unsigned)time(NULL));

    while(izbor != 'K' && izbor != 'k')
    {
        printf("\r\n\t\t********************");
        printf("\r\n\t\t***   IZBORNIK   ***");
        printf("\r\n\t\t********************");
        printf("\r\n");
        printf("\r\n\t\t1.\tPush na stog");
        printf("\r\n\t\t2.\tPop sa stoga");
        printf("\r\n\t\tk.\tKraj programa");
        printf("\r\n\r\nIzbor : ");
        scanf_s(" %c", &izbor, 1);

        switch(izbor)
        {
        case '1':
            if(n < max)
                n = Push(&S, GetValueFromRange(0, 10000), n);
            else
                printf("\r\nStog je popunjen!\r\n");
            PrintList(S.Next, n);
            break;
        case '2':
            if(n > 0)
                n = Pop(&S, n);
            PrintList(S.Next, n);
            break;
        case 'K':
        case 'k':
            printf("\r\nBye bye!\r\n");
            break;
        default:
            printf("\r\nPogresan izbor!\r\npokusajte ponovno.\r\n\r\n\r\n");
        }
    }


}

int GetValueFromRange(int min, int max)
{
    int x = 0;

    x = rand()%(max-min) + min;

    return x;
}

int Push(Position P, int x, int n)
{
    static Position last;
    Position q;

    q=(Position)malloc(sizeof(struct _Cvor));
    if(q)
    {
        if(P->Next == NULL)
            last = q;

        q->Element = x;

        printf("\r\nNa listu se sprema %d.", x);
        q->Next = P->Next;
        P->Next = q;

        last->Next = q;
        n++;
    }
    return n;
}

int Pop(Position P, int n)
{
    static Position last = NULL;
    Position tmp;

    if(P->Next != NULL)
    {

        tmp = P->Next;

        printf("\r\nSa liste se skida %d.", tmp->Element);

        P->Next = tmp->Next;

        if(last == NULL && n > 1)
        {
            while(P->Next != tmp)
                P = P->Next;
            last = P;
        }

        last->Next = tmp->Next;

        free(tmp);
        n--;
        if(n == 0)
            last = NULL;
    }
    else
        printf("\r\nLista je prazna.");

    return n;
}

void PrintList(Position P, int n)
{
    printf("\r\n\r\nU listi se nalaze %d elemenata:\r\n", n);
    while(n > 0)
    {
        printf(" %d", P->Element);
        P = P->Next;
        n--;
    }
}