本系列文章简要介绍链表的相关知识。

本文是系列文章的第三篇，将介绍在单向链表中删除节点的方法，并给出示例代码。 1 概述在单向链表中删除节点，首先要根据预先确定的节点标志，判断待删除节点是否存在于链表之中，如果链表中不存在该节点，则无需进行删除操作。如果该节点存在于链表之中，在删除该节点时，还需要区分以下两种情况：

待删除节点是链表的首节点；

待删除节点不是链表的首节点（即该节点是中间节点或末尾节点）。
下面通过伪代码的形式介绍在单向链表中删除节点的算法。

算法：DeleteLinkedlist(list,target)
目的：在单向链表中删除节点
前提：链表和要删除的节点信息
后续：无
返回：新链表
{
    if (list == null)           // empty list
    {
        // nothing to do
        return
    }
    
    cur <- list
    
    while (((*cur).num != (*target).num) && ((*cur).link != null))    // find target node location
    {
        pre <- cur
        cur <- (*cur).link
    }
    
    if ((*cur).num == (*target).num)    // target node in the list
    {
        if (list == cur)                // target node is the first node
        {
            list <- (*cur).link
        }
        else                            // target node is not the first node
        {
            (*pre).link <- (*cur).link
        }
    }
    else
    {
        // target node not found
    }
    
    return list
}

2 代码示例

根据上述内容，可以编写在单向链表中删除节点的示例代码。

示例代码的内容如下：

#include <stdio.h>
 
#define STRUCT_LEN sizeof(struct student)
 
struct student
{
    int stu_num;                /* student number */
    float stu_score;            /* student score */
    struct student* next;
};
 
int main()
{
    /* declaration of func */
    struct student * delete(struct student * head, struct student * target_node);
    void print(struct student * list);
 
    /* create a static linked list */
    struct student * list;
    struct student stu_1, stu_2, stu_3;
    stu_1.stu_num = 1;
    stu_1.stu_score = 88;
    stu_2.stu_num = 2;
    stu_2.stu_score = 66;
    stu_3.stu_num = 3;
    stu_3.stu_score = 100;
    list = &stu_1;
    stu_1.next = &stu_2;
    stu_2.next = &stu_3;
    stu_3.next = NULL;
 
    /* print linked list before deletion */
    printf("before deletion, ");
    print(list);
 
    /* create target node that to be deleted from linked list */
    struct student stu_del;
    stu_del.stu_num = 3;
    stu_del.stu_score = 0;         /* any value, because this item not compare */
    
    /* delete target node from linked list */
    list = delete(list, &stu_del);
 
    /* print linked list after deletion */
    printf("after deletion, ");
    print(list);
 
    return 0;
}
 
/*
** this is the delete linked list function.
*/
struct student * delete(struct student * head, struct student * target_node)
{
    struct student * cur;
    struct student * pre;
    struct student * target;
 
    cur = head;                 /* let cur point first node */
    target = target_node;       /* let target point the node that to be deleted */
 
    if (NULL == head)           /* empty list */
    {
        printf("list is null!\n");
        return head;
    }
 
    while (((*target).stu_num != (*cur).stu_num) && ((*cur).next != NULL))  /* find target node location */
    {
        pre = cur;
        cur = (*cur).next;
    }
 
    if ((*target).stu_num == (*cur).stu_num)        /* target node in the list */
    {
            if (head == cur)                        /* target node is the first node */
            {
                head = (*cur).next;
            }
            else                                    /* target node is not the first node */
            {
                (*pre).next = (*cur).next;
            }
    }
    else
    {
        printf("\ntarget node not found!\n\n");
    }
 
    return head;
}
 
/*
*  this is the print linked list content function.
*/
void print(struct student * list)
{
    struct student *walker;
    walker = list;
 
    printf("the linked list contents(student number and score) as followed:\n");
    printf("[student number] [student score]\n");
 
    while (walker != NULL)
    {
        printf("%d                %-f\n", (*walker).stu_num, (*walker).stu_score);
        walker = (*walker).next;
    }
    
    return;
}

上述代码的编译及运行结果如下：

说明：

上述代码中使用了待删除节点的学生学号信息“std_num”作为删除标志，除此之外的待删除节点的其他信息，不影响节点删除逻辑；
为了验证在待删除节点是链表首节点、链表中间节点和链表末尾节点的情况，可以通过修改待删除节点的结构体成员“stu_del.stu_num”的值，进行对应的测试；（上面已给出了这几种场景对应的测试结果）
为了简化代码内容，上述代码示例使用的是静态链表，即链表的所有节点都是在程序中定义的，节点的存储空间不是临时开辟的。

链表简介（三）——在单向链表中删除节点

2 代码示例