单链表基本算法

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

typedef int LinkType;
typedef struct LinkNode{
    LinkType data;
    struct LinkNode *next;
}LinkList;
//链表初始化
void  Linklistinit(LinkList **head)
{
    if (head == NULL)//输入不合法
        return;
    *head = NULL;
}
//链表尾部插入
void  LinkListPushBack(LinkList **head, LinkType valve)
{   
    LinkNode *new_Node = (LinkNode *)malloc(sizeof(LinkNode));
    new_Node->data = valve;
    new_Node->next = NULL;
    LinkNode *cur = *head;
    if (head == NULL)//输入不合法
        return;
    if ((*head) == NULL)//链表为空
    {
        *head = new_Node;
    }
    else
    {
        while (cur->next != NULL)
            cur = cur->next;
        cur->next = new_Node;
    }
}
//删除链表尾部元素
void LinkListPopBack(LinkNode** head)
{
    LinkNode *cur = *head;
    if (head == NULL)
        return;
    if (*head == NULL)
        return;
    if ((*head)->next == NULL)
    {
        free(*head);
        *head = NULL;
    }
    else
    {
        while (cur->next->next != NULL)
            cur = cur->next;
        free(cur->next);
        cur->next = NULL;
    }
}
//打印链表
void print(LinkList *head)
{
    LinkNode *cur = head;
    while (cur != NULL)
    {
        printf("%d ", cur->data);
        cur = cur->next;
    }
}
//链表头插
void LinkListPushFront(LinkNode** head, LinkType value)
{
    LinkNode *new_Node = (LinkNode *)malloc(sizeof(LinkNode));
    new_Node->data = value;
    new_Node->next = NULL;
    if (head == NULL)
        return;
    if (*head == NULL)
    {
        *head = new_Node;
    }
    else
    {
        new_Node->next = *head;
        *head =new_Node;
    }
}
//链表头删
void LinkListPopFront(LinkNode** head)
{
    LinkNode *cur = *head;
    if (head == NULL)
        return;
    if (*head == NULL)
        return;
    if ((*head)->next==NULL)
    {
        free(*head);
        *head = NULL;
    }
    else
    {
            cur = cur->next;
            free(*head);
            *head = cur;
    }
}
//查找元素在链表中的位置 ,返回这个值对应的节点地址 
LinkNode* LinkListFind(LinkNode* head, LinkType to_find)
{
    LinkNode *cur = head;
    if (head == NULL)
        return NULL;
    else
    {
        while (cur != NULL)
        {
            if (cur->data == to_find)
                return cur;
            cur = cur->next;
        }
    }
    return NULL;
}
//在指定pos节点的前面插入新节点
void LinkListInsertFront(LinkNode** head, LinkNode* pos, LinkType value)
{
    LinkNode *cur = *head;
    if (head == NULL)
        return; //不合法
    if (*head == NULL)
        return;//链表为空
    LinkNode *new_Node = (LinkNode *)malloc(sizeof(LinkNode));
    new_Node->data = value;
    new_Node->next = NULL;
    if (*head == pos) //如果pos是头结点
    {
        new_Node->next = *head;
        *head = new_Node;
    }
    else             //如果pos不是头结点
    {
        while (cur->next != pos)
            cur = cur->next;
        if (cur->next != NULL) //找到pos
        {
            new_Node->next = cur->next;
            cur->next = new_Node;
        }
        else            //没有找到pos
        {
            return;
        }

    }
}
void LinkListInsertAfter(LinkNode** head, LinkNode* pos, LinkType value)
{
    LinkNode *cur = *head;
    if (head == NULL)
        return;
    LinkNode *new_Node = (LinkNode *)malloc(sizeof(LinkNode));
    new_Node->data = value;
    new_Node->next = NULL;
    if (*head == pos)
    {
        new_Node->next = (*head)->next;//这两句话不能换位置
        (*head)->next = new_Node;       //
    }
    else
    {
        while (cur != pos)
            cur = cur->next;
        if (cur != NULL)
        {
            new_Node->next = cur->next;//
            cur->next = new_Node;
        }
    }
}
void LinkListErase(LinkNode** head, LinkNode* pos)
{//链表只有一个节点,pos是该节点,pos不是该节点
 //链表不止一个节点,pos是头节点,pos不是头结点
    LinkNode *cur = *head;
    if (head == NULL)
        return;
    if (*head == NULL)
        return;
    if ((*head)->next == NULL)
    {
        if (*head == pos)
        {
            free(*head);
            *head = NULL;
        }
        else
            return;
    }
    else
    {
        if (*head == pos)
            *head = cur->next;
        else
        {
            while (cur->next != pos)
                cur = cur->next;
            if (cur->next != NULL)  //
            {
                pos = cur->next;
                cur->next = pos->next;
                free(pos);
            }
            else
                return;
        }
    }
}
void LinkListRemove(LinkNode** head, LinkType to_delete)
{
    LinkNode *cur = *head, *dele;
    if (head == NULL)
        return;
    if (*head == NULL)
        return;
    if ((*head)->data == to_delete)
    {
        if ((*head)->next == NULL)
        {
            free(*head);
            *head = NULL;
        }
        else
        {
            dele = *head;
            *head = cur->next;
            free(dele);
        }
    }
    else
    {
        while (cur->next != NULL && cur->next->data != to_delete)//如果要查的数不存在
            cur = cur->next;
        if (cur->next != NULL)
        {
            dele = cur->next;
            cur->next = cur->next->next;
            free(dele);
        }
        else
            return;
    }
}
int LinkListEmpty(LinkNode* head)
{
    if (head == NULL)
        return 1;
    else
        return 0;
}

int main()
{
    int a;
    LinkList *L,*d;
    Linklistinit(&L);
    LinkListPushBack(&L, 9);
    LinkListPushBack(&L, 5);
    LinkListPushBack(&L, 7);
    LinkListPopBack(&L);
    LinkListPopFront(&L);
    LinkListPopFront(&L);
    d=LinkListFind(L,99);
    printf("%d  ", d);
    LinkListPushFront(&L, 6);
    LinkListInsertFront(&L, L->next->next, 6);
    LinkListInsertAfter(&L, L->next->next->next, 6);
    LinkListErase(&L, L->next->next);
    LinkListRemove(&L, 7);
    a=LinkListEmpty(L);
    printf("%d", a);
    print(L);
    system("pause");
    return 0;

}
单链表是一种线性数据结构,它由一系列节点组成,每个节点包含一个数据元素和指向下一个节点的指针。设计和实现单链表基本算法主要包括以下几个方面: 1. **创建链表**:初始化一个新的链表,通常通过节点head开始,其next指针为null。 ```python class Node: def __init__(self, data=None): self.data = data self.next = None def create_list(): head = Node() # 创建空链表 return head ``` 2. **添加元素**:在链表的末添加新节点,可以遍历整个链表找到最后一个节点然后添加。 ```python def append(head, data): new_node = Node(data) if not head: head = new_node else: current = head while current.next: current = current.next current.next = new_node return head ``` 3. **查找元素**:遍历链表,直到找到指定数据或遍历结束。 ```python def search(head, target): current = head while current and current.data != target: current = current.next if current: return True else: return False ``` 4. **除元素**:移除给定值的第一个匹配项,需要考虑节点的情况。 ```python def delete(head, data): if not head or head.data == data: if head is not None: head = head.next return head current = head while current.next and current.next.data != data: current = current.next if current.next: current.next = current.next.next return head ``` 5. **遍历链表**:用于打印或处理链表的所有节点。 ```python def traverse(head): current = head while current: print(current.data, end=" -> ") current = current.next print("None") ```
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