#include <bits\stdc++.h> 
using namespace std;
typedef long long ll;

 
struct Node{
    int key;
    Node *next,*prev;
};

Node *nil;

void init(){
    nil = (Node *) malloc(sizeof(Node));
    nil->next = nil;
    nil->prev = nil;
}

void insert(int key){
    Node *x = (Node *) malloc(sizeof
 
(Node));
    x->key = key;
    //在頭結點後添加元素 
    x->next = nil->next;
    nil->next->prev = x;
    nil->next = x;
    x->prev = nil;
}

Node *listSearch(int key){
    Node *cur = nil->next;  // 從頭結點後面的元素開始訪問 
    while(cur != nil && cur->key != key){
        cur = cur->next;
    }
    
 
return cur;
}

void deleteNode(Node *t){
    if(t == nil) return;  // t為頭結點時不作處理
    t->prev->next = t->next;
    t->next->prev = t->prev; 
    free(t);
}

void deleteFirst(){
    deleteNode(nil->next);
}

void deleteLast(){
    deleteNode(nil->prev);
}

void deleteKey(int key){
    
 
//刪除搜索到的結點
    deleteNode(listSearch(key)); 
}

void printList(){
    Node *cur = nil->next;
    int isf = 0;
    while(true){
        if(cur == nil) break;
        if(isf++ > 0) printf(" ");
        printf("%d",cur->key);
        cur = cur->next;
    }
    printf("\n");
}

int main() {


  return 0;
}
//  writen by zhangjiuding 

【模板】雙向鏈表