单链表

//初始化
struct ListNode 
{
    int val;
    ListNode *next;
    ListNode(int x) : val(x), next(NULL) {}
};
ListNode *head = new ListNode(-1);//建立头节点

//头插法插入元素
void headAdd(int x){
    if(head -> val == -1) head -> val = x;//空链表

    ListNode *node = new ListNode(x);
    node -> next = head;
    head= node;
}

//遍历
for(ListNode *p = head; p; p = p -> next){

}