c - 带 c 的双链表

Question

好的，现在我必须在 c 上创建双链表。有 7 个函数作用于 main。

追加。插入在。删除。打印。print_revers。新节点。新DLL。

我只能修改5个函数追加、insertAt、deleteAt、打印、print_reverse

终于我可以进行追加、打印、print_reverse但是，由于索引的原因，我无法进行 insertAt、deleteAt。

1.我不明白为什么代码

else {
    while (index-- >= 0) {
      temp = temp->next;
    }

使内存发生碰撞。为了使用索引，我需要移动节点来收集位置并连接到新节点。但它不起作用...

2.还有返回什么；的角色？我还没有见过这样的返回。

3.我如何使用索引进行deleteAt？我认为deleteAt和insertAt有非常相似的算法。所以我尝试首先插入并最后删除。但我写的效果不太好..

我可以在互联网上找到很多双链表的数据。但我找不到使用索引....我只听了两个月的c语言讲座，对spagettii代码感到抱歉...

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

typedef struct Node {
    int val;
    struct Node *prev;
    struct Node *next;
} Node;

typedef struct {
    Node *head;
    int size;
} DLL;

Node *newnode(int n)
{
    Node *temp = (Node *)malloc(sizeof(Node));
    temp->val = n;
    temp->prev = NULL;
    temp->next = NULL;
    return temp;
}

DLL *newDLL() {
    DLL *temp = (DLL *)malloc(sizeof(DLL));
    temp->head = NULL;
    temp->size = 0;
    return temp;
}

void append(DLL *list, Node *newnode) {
    struct Node* temp = list->head;
    struct Node* newNode = newnode;
    if (list->head == NULL) {
        list->head = newNode;
        list->size++;
        return;
    }
    while (temp->next != NULL) {
        temp = temp->next;
    }
    list->size++;
    temp->next = newNode;
    newNode->prev = temp;
}

void insertAt(DLL *list, int index, Node *newnode) {

    struct Node* temp = (Node *)malloc(sizeof(Node));

    if (index < 0 || index >= list->size + 1) {
        printf("out of range\n");
    }
    else if (index == 0) {
        newnode->next = list->head;
        list->head->prev = newnode;
        list->head = newnode;
    }
    else {
        while (index-- >= 0) {
          temp = temp->next;
        }

    temp->val = newnode->val;
    temp->next = list->head->next;
    list->head->next = temp;
    temp->prev = list->head;

    if (temp->next != NULL)
        temp->next->prev = temp;
    }
}

void deleteAt(DLL *list, int index) {
    //save reference to first link

    struct Node* temp = (Node *)malloc(sizeof(Node));

    //if only one link
    if (list->head->next == NULL) {
        list->head->prev = NULL;
    }
    else {
        list->head->next->prev = NULL;
    }

    list->head = list->head->next;
    //return the deleted link
    return;
}

void print(DLL *list) {
    struct Node* temp = list->head;
    printf("Forward: ");
    while (temp != NULL) {
        printf("[%d] ", temp->val);
        temp = temp->next;
    }
    printf("\n");
}

void print_reverse(DLL *list) {
    struct Node* temp = list->head;
    if (temp == NULL) return; // empty list, exit
    // Going to last Node
    while (temp->next != NULL) {
        temp = temp->next;
    }
    // Traversing backward using prev pointer
    printf("Reverse: ");
    while (temp != NULL) {
        printf("[%d] ", temp->val);
        temp = temp->prev;
    }
    printf("\n");
}

int main() {
    DLL *list = newDLL();
    int i;
    for (i = 1; i < 6; i++) {
        append(list, newnode(i));
    }

    print(list);
    deleteAt(list, -1);
    deleteAt(list, 5);
    deleteAt(list, 0);
    print(list);
    deleteAt(list, 2);
    print(list);
    deleteAt(list, 2);
    print(list);
    insertAt(list, -1, newnode(6));
    insertAt(list, 3, newnode(6));
    insertAt(list, 0, newnode(7));
    print(list);
    insertAt(list, 1, newnode(8));
    print(list);
    insertAt(list, 4, newnode(9));
    print(list);
    print_reverse(list);

    return 0;
}

Answer 1

您在索引处插入的部分有问题:

temp = malloc 错误，应该以 temp = head 开头。

在插入中:

temp->val = newnode->val;
temp->next = list->head->next;
list->head->next = temp;
temp->prev = list->head;

temp->next 不应该是 head->next，而应该是 newnode。 newnode->next 应该是 temp->next 等。