C Program For Implementing a Stack Using a Linked List

/*Implementing a Stack Using a Linked List*/

/* To read some numbers and print them in reverse order. For example, say we have these numbers:

36 15 52 23

And say we want to print the following:

23 52 15 36 */

#include <stdio.h>

#include <stdlib.h>

#define RogueValue -9999

typedef struct node {

   int num;

   struct node *next;

} Node, *NodePtr;

typedef struct stackType {

      NodePtr top;

} StackType, *Stack;

Stack initStack() {

      Stack sp = (Stack) malloc(sizeof(StackType));

      sp -> top = NULL;

      return sp;

}

int empty(Stack S) {

      return (S -> top == NULL);

} //end empty

void push(Stack S, int n) {

      NodePtr np = (NodePtr) malloc(sizeof(Node));

      np -> num = n;

      np -> next = S -> top;

      S -> top = np;

} //end push

int pop(Stack S) {

      if (empty(S)) return RogueValue;

      int hold = S -> top -> num;

      NodePtr temp = S -> top;

      S -> top = S -> top -> next;

      free(temp);

      return hold;

} //end pop

int main() {

      int n;

      Stack S = initStack();

      printf("Enter some integers, ending with 0\n");

      scanf("%d", &n);

      while (n != 0) {

            push(S, n);

            scanf("%d", &n);

      }

      printf("\nNumbers in reverse order\n");

      while (!empty(S))

            printf("%d ", pop(S));

      printf("\n");

}