1.4 双向循环链

// 该程序使用带头结点的双向循环链表
// 交换节点进行排序

//补充：locate & Insert

#include <stdio.h>
#include <stdlib.h>

typedef struct _Node{
    int data;
    struct _Node *next;
    struct _Node *prior;
}DNode;

DNode *createList(){
    DNode *head=(DNode *)malloc(sizeof(DNode));
    head->next=head->prior=head;
    return head;
}

//头是固定的使用头插法比较方便
void insertList(DNode *head,int data){
    DNode *p=(DNode *)malloc(sizeof(DNode));
    p->data=data;

    p->next=head->next;         //先改变p的指向，不影响原链表的指向关系
    p->prior=head;

    p->prior->next=p;              //利用已有的双向关系进行修改
    p->next->prior=p;
}

void traverseDList(DNode *head){
    DNode *p=head->next;
    DNode *p2=NULL;
    printf("Traverse:");
    while(p!=head){
        printf("%d ",p->data);
        p2=p;
        p=p->next;
    }
    printf("
");

    //Reverse
#if 1
    printf("Reverse:");
    while(p2!=head){
        printf("%d ",p2->data);
        p2=p2->prior;
    }
    printf("
");
#endif
}

void searchElem(DNode *head,int n){
    DNode *p=head->next;
    int flag=0;
    while(p!=head){
        if(p->data==n){
            flag=1;
            printf("Find elem addr:%p
",p);
        }
        p=p->next;
    }
    if(!flag){
        printf("Can not find elem %d !",n);
    }
}

int deleteElem(DNode *head,int n){
    DNode *p1=head->next;
    DNode *p2=head;
    while(p1!=head){
        if(p1->data==n){
            //delete elem
            p2->next=p1->next;
            p1->next->prior=p2;
            free(p1);
            printf("delete %d !
",n);
            return 1;
        }
        p2=p1;
        p1=p1->next;
    }
    return 0;
}

void swapNode(DNode *p2,DNode *p1){  //交换p2和它的下一个节点
    p2->prior->next=p1;
    p2->next=p1->next;
    p1->next=p2;
    
    p1->prior=p2->prior;
    p2->next->prior=p2;
    p2->prior=p1;
}

#if 1
int listNESort(DNode *head){         //先按从大到小排。小的(上浮)至尾部
    int flag;
    DNode *p1,*p2;
    p1=head->next;
    for(p1=p1->next;p1!=head;){
        flag=1;
        for(p2=head->next;p2!=p1;p2=p2->next){
            if((p2->data) > (p2->next->data)){
                swapNode(p2,p2->next);

                flag=0;

                if(p1->next==p2)              //交换p2和p2->next后，p1位置可能也变了
                    p1=p1->next;                //先把p1换回去，恢复p1在前p2在后
                p2=p2->prior;                   //p2退回去
                //traverseDList(head);   
            }
        }
        if(flag)p1=p1->next;
                //printf("2.p2:%d ,p1:%d
",p2->data,p1->data); 
    }
}
#endif

//void listDESort(DNode *head){  //Excheange Data
//}

int main(){
    DNode *head=createList();
    int i;
    for(i=1;i<=10;i++){
        insertList(head,i);
    }
#if 0
    insertList(head,1);
    insertList(head,3);
    insertList(head,5);
    insertList(head,7);
    insertList(head,2);
    insertList(head,4);
    insertList(head,6);
    insertList(head,8);
#endif
#if 0
    int find=7;
    searchElem(head,find);

    deleteElem(head,5);
    traverseDList(head);
#endif

#if 0
    DNode *p=head->next;
    p=p->next;
    p=p->next;
    swapNode(p,p->next);
#endif

    listNESort(head);
    traverseDList(head);
    return 0;
}