C - Veri Yapıları (Yığınlar) Push-Pop-Peek İşlemleri

#include<stdio.h>
#include<stdlib.h>

struct node {	
	int data;
	struct node * next;	
};

struct node * temp = NULL;
struct node * top = NULL;

v o i d push(int veri) { 
	
	struct node * eleman = (struct node *) malloc (sizeof(struct node));
	eleman->data = veri;
	
	if (top == NULL) { 
		top = eleman;
		top->next = NULL;
	}
	else {
		eleman->next = top; 
		top = eleman; 
	} 
}

v o i d  pop() {
	
	if (top == NULL) {
		printf("Silinecek Eleman Bulunamadi..\n");
	}
	else {
		printf("%d elemani yigindan cikarildi. \n",top->data);  
		temp = top->next; 
		free(top);
		top = temp;
	}
}

v o i d print() { 
	system("cls");
	if ( top == NULL ) {
		printf("Yazdirilacak Eleman Yok..\n");
	}
	else {
		temp = top;
		while (temp->next!=NULL) {
			printf("%d\n",temp->data);
			temp = temp->next;
		}
		printf("%d\n",temp->data);
	}
}

v o i d  peek () {
	if ( top == NULL ) {
		printf("Yigin bos..\n");
	}
	else {
		printf("Yiginda ki en ust eleman : %d \n",top->data);
	}
}


int main () {

	int secim,sayi;
	
	while (1) {
		printf("\nSTACK ( YIGIN ) \n");
		printf("1--> Push islemi \n");
		printf("2--> Pop islemi \n");
		printf("3--> Print islemi \n");
		printf("4--> Peek islemi (En ust deger) \n");
		printf("5--> Cikis islemi \n\n");
		
		printf("Seciminizi Yapin(1-5):");
		scanf ("%d",&secim);
		switch(secim) {
			case 1: 
			printf("Yigina Eklenecek sayi:");
			scanf("%d",&sayi);
			push(sayi);
			break;
			
			case 2:
			pop();
			break;
			
			case 3:
			print();
			break;
			
			case 4:
			peek();
			break;
			
			case 5:
			return 0;
		}
	}
	
	return 0;
}