15、循环链表

将单链表中终端结点的指针端由空指针改为指向头结点，就使整个单链表形成一个环，这种头尾相接的链表称为单循环链表，简称循环链表。

CircleLinkList.h

#ifndef CIRCLELINKLIST_H
#define CIRCLELINKLIST_H

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


//链表小结点
typedef struct CIRCLELINKNODE {
    struct CIRCLELINKNODE* next;
}CircleLinkNode;

//链表结构体
typedef struct CIRCLELINKLIST {
    CIRCLELINKNODE head;
    int size;
}CircleLinkList;

//编写针对链表结构体操作的API函数

#define TRUE 1
#define FALSE 0


//比较回调
typedef int(*COMPARENODE)(CircleLinkNode*, CircleLinkNode*);
//打印回调
typedef void(*PRINTNODE)(CircleLinkNode*);


//初始化函数
CircleLinkList* Init_CircleLinkList();
//插入函数
void Insert_CircleLinkList(CircleLinkList* clist,int pos, CircleLinkNode* data);
//获得第一个元素
CircleLinkNode* Front_CircleLinkList(CircleLinkList* clist);
//根据位置删除
void RemoveByPos_CircleLinkList(CircleLinkList* clist,int pos);
//根据值去删除
void RemoveByValue_CircleLinkList(CircleLinkList* clist, CircleLinkNode* data, COMPARENODE compare);
//获得链表的长度
int Size_CircleLinkList(CircleLinkList* clist);
//判断是否为空
int IsEmpty_CircleLinkList(CircleLinkList* clist);
//查找
int Find_CircleLinkList(CircleLinkList* clist, CircleLinkNode* data, COMPARENODE compare);
//打印结点
void Print_CircleLinkList(CircleLinkList* clist,PRINTNODE print);
//释放内存
void FreeSpace_CircleLinkList(CircleLinkList* clist);


#endif

CircleLinkList.c

#include"CircleLinkList.h"



//初始化函数
CircleLinkList* Init_CircleLinkList() {

    CircleLinkList* clist = (CircleLinkList*)malloc(sizeof(CircleLinkList));
    clist->head.next = &(clist->head);
    clist->size = 0;

    return clist;
}
//插入函数
void Insert_CircleLinkList(CircleLinkList* clist, int pos, CircleLinkNode* data) {
    if (clist == NULL) {
        return;
    }
    if (data == NULL) {
        return;
    }
    if (pos<0 || pos>clist->size) {
        pos = clist->size;
    }
    //根据位置查找前一个结点
    //辅助指针变量
    CircleLinkNode* pCurrent = &(clist->head);
    for (int i = 0; i < pos; i++) {
        pCurrent = pCurrent->next;
    }
    //插入新元素
    data->next = pCurrent->next;
    pCurrent->next = data;

    clist->size++;
}
//获得第一个元素
CircleLinkNode* Front_CircleLinkList(CircleLinkList* clist) {
    return clist->head.next;
}
//根据位置删除
void RemoveByPos_CircleLinkList(CircleLinkList* clist, int pos) {
    if (clist == NULL) {
        return;
    }
    if (pos<0 || pos>clist->size) {
        return;
    }
    //根据pos找上一个结点
    //辅助指针变量
    CircleLinkNode* pCurrent = &(clist->head);
    for (int i = 0; i < pos; i++) {
        pCurrent = pCurrent->next;
    }

    //缓存当前结点的下一个结点
    CircleLinkNode* pNext = pCurrent->next;
    pCurrent->next = pNext->next;

    clist->size--;

}
//根据值去删除
void RemoveByValue_CircleLinkList(CircleLinkList* clist, CircleLinkNode* data, COMPARENODE compare) {
    if (clist == NULL) {
        return;
    }
    if (data == NULL) {
        return;
    }
    //这个是循环链表，不能一直循环
    CircleLinkNode* pPrev = &(clist->head);
    CircleLinkNode* pCurrent = pPrev->next;
    int i = 0;
    for (; i < clist->size; i++) {
        if (compare(pCurrent,data) == TRUE) {
            pPrev->next = pCurrent->next;
            break;
        }
        pPrev = pCurrent;
        pCurrent = pPrev->next;
    }

    clist->size--;

}
//获得链表的长度
int Size_CircleLinkList(CircleLinkList* clist) {
    return clist->size;
}
//判断是否为空
int IsEmpty_CircleLinkList(CircleLinkList* clist) {
    if (clist->size == 0) {
        return TRUE;
    }
    return FALSE;
}
//查找
int Find_CircleLinkList(CircleLinkList* clist, CircleLinkNode* data, COMPARENODE compare) {
    if (clist == NULL) {
        return FALSE;
    }
    if (data == NULL) {
        return FALSE;
    }
    CircleLinkNode* pCurrent = clist->head.next;
    int flag = -1;
    for (int i = 0; i < clist->size; i++) {
        if (compare(pCurrent, data) == TRUE) {
            flag = i;
            break;
        }
        pCurrent = pCurrent->next;
    }

    return flag;
}
//打印结点
void Print_CircleLinkList(CircleLinkList* clist, PRINTNODE print) {
    if (clist == NULL) {
        return;
    }
    CircleLinkNode* pCurrent = clist->head.next;
    for (int i = 0; i < clist->size; i++) {
        if(pCurrent==&(clist->head)){
            pCurrent = pCurrent->next;
            printf("-----------------
");
        }
        print(pCurrent);
        pCurrent = pCurrent->next;
    }
}
//释放内存
void FreeSpace_CircleLinkList(CircleLinkList* clist) {
    if (clist == NULL) {
        return;
    }
    free(clist);
}

main.c

#define _CRT_SECURE_NO_WARNINGS
#include<stdio.h>
#include<stdlib.h>
#include<string.h>
#include"CircleLinkList.h"

typedef struct PERSON {
    CircleLinkNode* node;
    char name[64];
    int age;
    int score;
}Person;

void MyPrint(CircleLinkNode* data) {
    Person* p = (Person*)data;
    printf("Name:%s  Age:%d  Score:%d
",p->name,p->age,p->score);
}

int MyCompare(CircleLinkNode* data1, CircleLinkNode* data2) {
    Person* p1 = (Person*)data1;
    Person* p2 = (Person*)data2;
    if (strcmp(p1->name, p2->name) == 0 && p1->age == p2->age && p1->score == p2->score) {
        return TRUE;
    }
    return FALSE;
}

int main() {

    //创建循环链表
    CircleLinkList* clist = Init_CircleLinkList();
    //创建数据
    Person p1, p2, p3, p4, p5;
    strcpy(p1.name, "aaa");
    strcpy(p2.name, "bbb");
    strcpy(p3.name, "ccc");
    strcpy(p4.name, "ddd");
    strcpy(p5.name, "eee");

    p1.age = 15;
    p2.age = 16;
    p3.age = 17;
    p4.age = 18;
    p5.age = 19;

    p1.score = 55;
    p2.score = 60;
    p3.score = 70;
    p4.score = 80;
    p5.score = 90;

    //数据入链表
    Insert_CircleLinkList(clist, 100, (CircleLinkNode*)&p1);
    Insert_CircleLinkList(clist, 100, (CircleLinkNode*)&p2);
    Insert_CircleLinkList(clist, 100, (CircleLinkNode*)&p3);
    Insert_CircleLinkList(clist, 100, (CircleLinkNode*)&p4);
    Insert_CircleLinkList(clist, 100, (CircleLinkNode*)&p5);


    //打印
    Print_CircleLinkList(clist, MyPrint);

    Person pDel;
    strcpy(pDel.name, "ccc");
    pDel.age = 17;
    pDel.score = 70;
    //根据值删除
    RemoveByValue_CircleLinkList(clist, (CircleLinkNode*)&pDel, MyCompare);
    //打印
    printf("------------------
");
    Print_CircleLinkList(clist, MyPrint);


    //释放内存
    FreeSpace_CircleLinkList(clist);



    system("pause");
    return 0;
}

运行结果：