연결리스트로 Stack 구현

#include <stdio.h>
#include <stdlib.h>
#define STACK_ERROR 60000

typedef int element;

typedef struct stacknode{
	element data;
	struct stacknode* link;
}StackNode;

typedef struct{
	int numOfNode;
	StackNode* top;
}LinkedStack;

LinkedStack* createStack(){
	LinkedStack *s=(LinkedStack*)malloc(sizeof(LinkedStack));
	s->numOfNode=0;
	s->top=NULL;
	return s;
}

int isEmpty(LinkedStack *s){
	if(s->top==NULL) return 1;
	else return 0;
}

int push(LinkedStack *s, element data){
	StackNode *newNode=(StackNode*)malloc(sizeof(StackNode));
	if(newNode==NULL){
		printf("stack overflow\n");
		return STACK_ERROR;
	}
	newNode->data=data;

	newNode->link=s->top;
	s->top=newNode;
	s->numOfNode++;
	return 1;
}

element pop(LinkedStack *s){
	StackNode *temp;
	element data;
	temp=s->top;
	if(isEmpty(s)){
		printf("stack underflow\n");
		return STACK_ERROR;
	}
	s->top=temp->link;
	s->numOfNode--;

	data=temp->data;
	free(temp);
	return data;
}

element peek(LinkedStack *s){
	if(isEmpty(s)){
		printf("Stack is Empty\n");
		return STACK_ERROR;
	}
	return s->top->data;
}

void printStack(LinkedStack *s){
	StackNode *temp;
	temp=s->top;
	while(temp!=NULL){
		printf("%d\n",temp->data);
		temp=temp->link;
	}
	printf("\n");
}

int main(){
	LinkedStack *s1, *s2;
	s1=createStack();
	s2=createStack();

	push(s1,10);
	push(s2,10);
	printStack(s1);
	push(s1,100);
	printStack(s1);
	pop(s1);
	printStack(s1);

	pop(s1);
	return 0;
}