【 数据结构（C语言）】线性表——双向链表和双向循环链表

双向链表：每个数据结点中都有两个指针，分别指向直接后继和直接前驱。所以，从双向链表中的任意一个结点开始，都可以很方便地访问它的前驱结点和后继结点

1.双向链表的基本实现（带头尾指针）

/**
**  2017.11.1
**  Ahthor:799
**  双向链表
**
***/
#include <bits/stdc++.h>
using namespace std;
#define ElemType  int
#define Status int
#define ERROR -1
#define OK 1

typedef struct LNode
{
   ElemType data;
   struct  LNode *prev;
   struct  LNode *next;
};
typedef struct DLinkList
{
    int len;
    LNode  *head,*tail;
};
void InitLinkList (DLinkList &L)
{
    L.len = 0;
    L.head = (LNode * )malloc(sizeof(LNode));
    L.tail = (LNode * )malloc(sizeof(LNode));
    L.head->next = L.tail;
    L.head->prev = NULL;
    L.tail->prev = L.head;
    L.tail->next = NULL;
    return ;
}
int GetLengthLinkList(DLinkList &L)
{
    LNode *index = L.head->next;
    int ct = 0;
    while (index != L.tail)
    {
        ct++;
        index = index->next;
    }
    return ct;
}
LNode* GetLinkListElem(DLinkList &L,int i)
{
    LNode *index = L.head;
    int ct = 0;
    while (ct < i)
    {
        ct++;
        index = index->next;
    }
    return index;
}
Status InsertLinkList(DLinkList &L,int i,ElemType data)///* 前插入
{
    if (i <0 || i > GetLengthLinkList(L) + 1) return ERROR;
    LNode *pointer =  GetLinkListElem(L,i);
    LNode *newnode  = (LNode *)malloc(sizeof(LNode)) ;
    newnode->data = data;
    newnode->prev = pointer->prev;
    pointer->prev->next = newnode;
    newnode->next = pointer;
    pointer->prev = newnode;
    L.len++;
    return OK;
}
Status DeteleLinkListByPos(DLinkList &L,int i,ElemType &e)/// 按位删除
{
    LNode *pointer = GetLinkListElem(L,i);
    e = pointer->data;
    pointer->prev->next = pointer->next;
    pointer->next->prev = pointer->prev;
    return OK;
}
Status DeteleLinkListByVal(DLinkList &L,ElemType e)/// 按位删除
{
    LNode *pointer = L.head->next;
    for (;pointer != L.tail; pointer = pointer->next)
    {
        if (pointer->data == e)
        {
            pointer->prev->next = pointer->next;
            pointer->next->prev = pointer->prev;
        }
    }
    return OK;
}
void TrverseLinkList(DLinkList &L)
{
    LNode *index = L.head->next;;
    for (; index != L.tail; index = index->next )
    {
        cout<<index->data<<" ";
    }
    cout<<endl;
}
int main()
{
    int n;
    cin>>n;

    DLinkList *Dk = (DLinkList *) malloc(sizeof(DLinkList));
    InitLinkList(*Dk);
    for (int i=1; i <= n; i++)
    {
        int tmp;
        cin>>tmp;
        InsertLinkList(*Dk,i,tmp);
    }
    TrverseLinkList(*Dk);
    int pos,val;
    cin>>val;
    DeteleLinkListByVal(*Dk,val);
    TrverseLinkList(*Dk);
}

　2.双向循环链表（带头结点）

/**
**  2017.11.1
**  Ahthor:799
**  循环双向链表
**
***/
#include <bits/stdc++.h>
using namespace std;
#define ElemType  int
#define Status int
#define ERROR -1
#define OK 1

typedef struct LNode
{
   ElemType data;
   struct  LNode *prev;
   struct  LNode *next;
};
typedef struct DLinkList
{
    int len;
    LNode  *head;
};
void InitLinkList (DLinkList &L)
{
    L.len = 0;
    L.head = (LNode * )malloc(sizeof(LNode));
    L.head->next = L.head;
    L.head->prev = L.head;
    return ;
}
int GetLengthLinkList(DLinkList &L)
{
    LNode *index = L.head->next;
    int ct = 0;
    while (index != L.head)
    {
        ct++;
        index = index->next;
    }
    return ct;
}
LNode* GetLinkListElem(DLinkList &L,int i)
{
    LNode *index = L.head;
    int ct = 0;
    while (ct < i)
    {
        ct++;
        index = index->next;
    }
    return index;
}
Status InsertLinkList(DLinkList &L,int i,ElemType data)///* 前插入
{
    if (i <0 || i > GetLengthLinkList(L) + 1) return ERROR;
    LNode *pointer =  GetLinkListElem(L,i);
    LNode *newnode  = (LNode *)malloc(sizeof(LNode)) ;
    newnode->data = data;
    newnode->prev = pointer->prev;
    pointer->prev->next = newnode;
    newnode->next = pointer;
    pointer->prev = newnode;
    L.len++;
    return OK;
}
Status DeteleLinkListByPos(DLinkList &L,int i,ElemType &e)/// 按位删除
{
    LNode *pointer = GetLinkListElem(L,i);
    e = pointer->data;
    pointer->prev->next = pointer->next;
    pointer->next->prev = pointer->prev;
    free(pointer);
    return OK;
}
Status DeteleLinkListByVal(DLinkList &L,ElemType e)/// 按位删除
{
    LNode *pointer = L.head->next;
    for (;pointer != L.head; pointer = pointer->next)
    {
        if (pointer->data == e)
        {
            pointer->prev->next = pointer->next;
            pointer->next->prev = pointer->prev;
            free(pointer);
        }
    }
    return OK;
}
void TrverseLinkList(DLinkList &L)
{
    LNode *index = L.head->next;;
    for (; index != L.head; index = index->next )
    {
        cout<<index->data<<" ";
    }
    cout<<endl;
}
int main()
{
    int n;
    cin>>n;

    DLinkList *Dk = (DLinkList *) malloc(sizeof(DLinkList));
    InitLinkList(*Dk);
    for (int i=1; i <= n; i++)
    {
        int tmp;
        cin>>tmp;
        InsertLinkList(*Dk,i,tmp);
    }
    TrverseLinkList(*Dk);
    int pos,val;
    cin>>val;
    DeteleLinkListByVal(*Dk,val);
    TrverseLinkList(*Dk);
}