[c++] 구조체 포인터 node 관리 - insert

#include<stdio.h>
#include<stdlib.h>
#include<conio.h>
struct node
{
	int data;
	struct node *next;
};
struct node *node_insert(struct node *head, int cur_data,int insert_data);
void list_print(struct node *);
void main(){
	struct node a, b, c;
	struct node *head;
	head=&a;
	a.data = 10;
	b.data = 20;
	c.data = 30;
	a.next= &b;
	b.next = &c; 
	c.next = NULL; 
	list_print(head);
	head = node_insert(head, 20, 5);
	list_print(head);
}
void list_print(struct node *head){ 
	for(; head; head=head->next)
	printf(" %d\n", head->data);
}
struct node *node_insert(struct node *head, int cur_data, int insert_data)
{
	struct node *ptr,*tmp,*newnode;
	newnode=(struct node *)malloc(sizeof(struct node));
	newnode->data = insert_data;
	newnode->next = NULL;
	ptr=tmp=head;
	if(ptr->data==cur_data)
	{
		newnode->next=ptr;
		head=newnode;
	}
	else
	{
		while(ptr->data != cur_data)
		{
			tmp=ptr;
			ptr=ptr->next;
			
		}
		newnode->next=ptr;
		tmp->next=newnode;
	}
	printf("%d 전에 %d 삽입\n",cur_data,insert_data);
	return head;
}