stack.c

This program use for topological sorting

#define TRUE 1
#define FALSE 0
#define STACK_SIZE 50   /*stack at most 50 elem*/
#define STACK_ELEMENT_TYPE char        /* Needs to change type for different program !*/

typedef struct {
        STACK_ELEMENT_TYPE elem[STACK_SIZE];
        int top;
}seqstack;

void Initstack(seqstack *S){
     S->top=-1;
}

int Push(seqstack *S, STACK_ELEMENT_TYPE x){
    if (S->top==STACK_SIZE)
        return(FALSE);      /*stack is full*/
    S->top++;
    S->elem[S->top] = x;
    return (TRUE);
}

int Pop(seqstack *S,STACK_ELEMENT_TYPE *x){
    if(S->top==-1)
       return(FALSE);   /*stack is empty*/
    *x=S->elem[S->top];
    S->top--;
    return (TRUE);
}

int Gettop(seqstack *S, STACK_ELEMENT_TYPE *x){
    if(S->top==-1)
       printf("There is no element!\n");
    *x=S->elem[S->top];
    return (TRUE);
}