数据结构与算法 — 双向链表

双向链表

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双向链表的结构

双向链表的结点包括三个部分：前驱指针域、数据域和后继指针域：

• 前驱指针域，又称为左链指针，用于存放一个指针，该指针指向上一个结点的开始存储地址；
• 数据域，用于存储该结点的数据元素，数据元素类型由应用问题决定。
• 后继指针域，又称为右链指针，用于存放一个指针，该指针指向下一个结点的开始存储地址。

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双向链表的实现

结构体设计

typedef struct Node {
    ElemType data;
    struct Node *prior;
    struct Node *next;
} Node;

typedef struct Node * LinkList;

双向链表的创建

Status CreateLinkList(LinkList *L) {
    *L = (LinkList)malloc(sizeof(Node));
    if (*L == NULL) return ERROR;
    (*L)->prior = NULL;
    (*L)->next = NULL;
    (*L)->data = -1;
    
    LinkList p = *L;
    for (int i = 1; i <= 10; i++) {
        LinkList temp = (LinkList)malloc(sizeof(Node));
        if (temp == NULL) return ERROR;
        temp->data = i;
        temp->prior = NULL;
        temp->next = NULL;
        
        p->next = temp;
        temp->prior = p;
        p = p->next;
    }
    return OK;
}

双向链表的插入

Status LinkListInsert(LinkList *L, int place, int num) {
    if (place < 1) return ERROR;
    LinkList temp = (LinkList)malloc(sizeof(Node));
    temp->prior = NULL;
    temp->next = NULL;
    temp->data = num;
    
    LinkList p = *L;
    for (int i = 1; i < place && p != NULL; i++) {
        p = p->next;
    }
    
    if (p == NULL) return ERROR;
    
    if (p->next == NULL) {
        p->next = temp;
        temp->prior = p;
    } else {
        temp->next = p->next;
        p->next->prior = temp;
        p->next = temp;
        temp->prior = p;
    }
    
    return OK;
}

双向链表的删除

删除指定位置

Status LinkListDelete(LinkList *L, int place, ElemType *e) {
    if (place < 1 || *L == NULL) return ERROR;

    LinkList p = *L;
    for (int i = 1; i < place && p != NULL; i++) {
        p = p->next;
    }
    if (p == NULL) return ERROR;
    
    LinkList deleteItem = p->next;
    *e = deleteItem->data;

    p->next = deleteItem->next;
    if (deleteItem->next != NULL) {
        deleteItem->next->prior = p;
    }
    free(deleteItem);
    
    return OK;
}

删除指定元素

Status LinkListDeleteValue(LinkList *L, ElemType value) {
    LinkList p = *L;
    while (p) {
        if (p->data == value) {
            p->prior->next = p->next;
            if (p->next != NULL) {
                p->next->prior = p->prior;
            }
            free(p);
            break;
        }
        p = p->next;
    }
    return OK;
}

双向链表的查找

int LocateElem(LinkList L, ElemType value) {
    LinkList p = L->next;
    int i = 1;
    while (p) {
        if (p->data == value) {
            return i;
        }
        i++;
        p = p->next;
    }
    return ERROR;
}

双向链表的遍历输出

void TraverseLinkList(LinkList L) {
    LinkList temp = L->next;
    if(temp == NULL){
        printf("打印的双向链表为空!\n");
        return;
    }
    
    while (temp) {
        printf("%d_%d_%d  ", temp->prior ? temp->prior->data : -1, temp->data, temp->next ? temp->next->data : -1);
        temp = temp->next;
    }
    printf("\n");
}

双向循环链表

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双向循环链表和双向链表的唯一区别在于循环，尾结点的next指针会指向头结点，头结点的prior指针会指向尾结点

双向循环链表的创建

Status CreateLinkList(LinkList *L) {
    *L = (LinkList)malloc(sizeof(Node));
    if (*L == NULL) return ERROR;
    (*L)->next = *L;
    (*L)->prior = *L;
    (*L)->data = -1;
    
    LinkList p = *L;
    for (int i = 10; i < 15; i++) {
        LinkList temp = (LinkList)malloc(sizeof(Node));
        if (temp == NULL) return ERROR;
        temp->data = i;
        
        p->next = temp;
        temp->prior = p;
        temp->next = (*L);
        
        p = p->next;
    }
    return OK;
}

双向循环链表插入

Status LinkListInsert(LinkList *L, int place, ElemType num) {
    if (place < 1) return ERROR;
    
    LinkList p = *L;
    int i = 1;
    while (i < place && p->next != *L) {
        p = p->next;
        i++;
    }
    
    if (i > place) return ERROR;
    
    LinkList temp = (LinkList)malloc(sizeof(Node));
    if (temp == NULL) return ERROR;
    temp->data = num;
    temp->next = p->next;
    p->next = temp;
    temp->prior = p;
    if (p->next != *L) {
        temp->next->prior = temp;
    } else {
        (*L)->prior = temp;
    }
    
    return OK;
}

双向循环链表的删除

Status LinkListDelete(LinkList *L, int place, ElemType *e) {
    if (place < 1 || *L == NULL) return ERROR;

    LinkList p = (*L)->next;
    if (p->next == *L) {
        free(*L);
        *L = NULL;
        return OK;
    }
    
    int i = 1;
    while (i < place && p->next != *L) {
        p = p->next;
        i++;
    }
    
    if (i > place) return ERROR;
    *e = p->data;

    p->prior->next = p->next;
    p->next->prior = p->prior;

    free(p);
    return OK;
}

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Demo：https://github.com/ShoukaiWang/DataStructuresAndAlgorithms