[BS] Stack ADT

Stacks are implemented in two ways: single-linked lists, arrays

This article is the basic operation of the single-linked list implementation method.

Data:

struct Node{elementtype Element; Ptrtonodenext;};

Data type:

typedef int ELEMENTTYPE;TYPEDEF struct Node *ptrtonode;typedef ptrtonode Stack;

Basic Operation:

/* Return 1 if stack is null */intisempty (stack S) {return s->next = = NULL;}

NOTICE this FUNCTION

/* Create a void stack */stackcreatestack (void) {stack s;/* s point to heap */s = malloc (sizeof (struct Node)); if (s = = NULL) FatalError ("Out of space!!!"); S->next = NULL; Makeempty (s); return s;}

/* Make a stack empty */voidmakeempty (stack S) {/*if (S = = NULL) Error ("must use Createstack first"); Elsewhile (! IsEmpty (s)) Pop (s); */if (s! = NULL) while (! IsEmpty (s)) Pop (s), else/* S = = NULL */error ("must use Createstack first");}

/* Push x into stack s */voidpush (ElementType x, Stack s) {Ptrtonode Tmpcell; Tmpcell = malloc (sizeof (struct Node)), if (Tmpcell = = NULL) fatalerror ("Out of space!!!"); Else{tmpcell->element = X; Tmpcell->next = s->next; S->next = Tmpcell;}}

/* Abtain The top element of the stack s */elementtypetop (stack s) {if (! IsEmpty (S)) return s->next->element; Error ("Empty stack"), return 0;/* return value used to avoid warning */}

/* Pop The top element of the stack s */voidpop (stack s) {Ptrtonode firstcell;if (IsEmpty (S)) Error ("Empty stack"); else{f Irstcell = s->next; S->next = S->next->next;free (FirstCell);}}

/* Dispose stack */voiddisposestack (Stack S) {makeempty (s); free (s);}

/* Print All the elements of the stack */voidprintstack (stack S) {    stack sTmp;    STMP = S;    while (stmp->next! = NULL)    {        printf ("%d", stmp->next->element);        STMP = stmp->next;    }}

NOTICE this FUNCTION

/* Main function */intmain () {    int ireturn;    Stack Sa = Createstack ();    Push (1, Sa);    Push (2, Sa);    Push (3, Sa);    Push (4, Sa);    Push (5, Sa);    Pop (Sa);    Pop (Sa);    Printstack (Sa);    return 0;}

It is not difficult for a careful reader to notice (this remark) that the two function is preceded by the NOTICEthis function, in the first function:

/* Create a void stack */stackcreatestack (void) {stack s;/* s point to heap */s = malloc (sizeof (struct Node)); if (s = = NULL) FatalError ("Out of space!!!"); S->next = NULL; Makeempty (s); return s;}

Stack s;/* S point to heap */

And look at the second function. MainFunction:

/* Main function */intmain () {    int ireturn;    Stack Sa = Createstack ();    Push (1, Sa);    Push (2, Sa);    Push (3, Sa);    Push (4, Sa);    Push (5, Sa);    Pop (Sa);    Pop (Sa);    Printstack (Sa);    return 0;}

Stack Sa = Createstack ();

Here Createstack ()is called, the function is returned with a return value, and a pointer is returned, note: The function cannot return a pointer to the stack memory!

But the pointer here is pointing to heap memory? So you can go back? The above test can be done normally!

[BS] Stack ADT