Mine

#include <stdio.h>
#include <stdlib.h>
#define MAXSTOG 20

int dodaj (char *stog1, char *stog2, int n, int *vrh);
int skini (char *stog1, char *stog2, int *vrh);
int premjesti (char *stog1, char *stog2, int n);

int main()
{
    char stog1[MAXSTOG];
    char stog2[MAXSTOG]={'\0'};

    printf("Unesi string u stog1: ");
    fgets(stog1, sizeof(stog1), stdin);
    stog1[strlen(stog1)-1]='\0';
    
    premjesti (stog1, stog2, MAXSTOG);
    
    printf("Prvi stog: %s\n", stog1);
    printf("Drugi stog: %s\n", stog2);
    
    getche();
    return 0;
}

int premjesti (char *stog1, char *stog2, int n) {
    int i=0, vrh=-1;
    char *pom;
    pom=stog1;

    while (*pom) {
        if(dodaj(pom, stog2, MAXSTOG, &vrh)==0) return 0;
        pom++;
    }
    while((vrh)>=0)
        if(skini(&stog1[i++], stog2, &vrh)==0) return 0;
}

int dodaj (char *stog1, char *stog2, int n, int *vrh) {
    if (*vrh >= n-1){
        return 0;
    }
    (*vrh)++;
    stog2[*vrh] = *stog1;
    return 1;
}

int skini (char *stog1, char *stog2, int *vrh) {
    if (*vrh < 0) return 0;
    *stog1 = '\0';
    (*vrh)--;
    return 1;
}