c++中关于双向链表的问题

#ifndef _DoubleList_h_
#define _DoubleList_h_

#include <stdio.h>
#include <stdlib.h>
typedef struct DNode//节点的定义
{
int x;
struct DNode *prior,*next;
}DNode;

typedef struct Header//头节点的定义
{
int length;
DNode *next;
}Header;

Header Init_List()//初始化一个双向链表
{
Header header;
header.length = 0;
header.next = NULL;
return header;
}
Header ListInsert(Header &header,int i,DNode &e)//在位置i插入指定元素e
{
if(i>header.length)
{
printf("please input suit num");
}
DNode *current=(DNode*)&header;
int j = 0;
if (header.next == NULL)
{
header.next=&e;
e.next =NULL;
e.prior=NULL;
header.length ++;
return header;
}
else if (i == header.length)
{
e.next = NULL;
e.prior = current;
current->next = &e;
header.length ++;
return header;
}
else
{
for (j=0;j<i;i++)
{
current=current->next;
}
e= *(current->next->prior);
e.next = current->next ;
*(current->next)= e;
e.prior = current;
header.length++;
return header;
}
}
#endif

int main()
{
DNode n1,n2,n3,n4;
n1.x = 1;
n2.x = 2;
n3.x = 3;
Header N;
N=Init_List();

N=ListInsert(N,0,n1);
printf("%d\n",N.next->x);

N=ListInsert(N,1,n2);
printf("%d",N.next->next->x);

N=ListInsert(N,1,n3);
printf("%d",N.next->next->next->next );
}
在打印第二个数时出现Program received signal SIGSEGV, Segmentation fault求教