如何删除C语言中从drivers.txt加载的链表里指定车队的车手节点

现有代码已知问题 #

• 加载函数drivers_load中，重置索引i=0的逻辑写在case 2的break之后，永远不会执行，导致无法正确读取多个车手数据
• 打印函数drivers_print中结构体成员引用错误，定义的是name/team，代码中错误写为presenter/birth_number
• 删除函数存在核心逻辑错误：
  • 未处理头节点即为待删除节点的场景，传入一级指针无法将修改后的头节点返回给调用方
  • 遍历未记录前驱节点，无法正确修改链表关联关系
  • 删除逻辑固定操作头节点的后继节点，和实际匹配到的待删节点无关
  • 未释放name/team指向的堆内存，存在内存泄漏
  • 使用了未定义的类型node_t

实现思路 #

1. 删除函数采用返回新头节点的方式处理头节点被删除的场景
2. 遍历链表同时记录当前节点和前驱节点
3. 匹配到待删除节点时：
   • 若为头节点，直接将头指针后移
   • 若为普通节点，将前驱节点的next指向当前节点的next
   • 依次释放当前节点的name、team内存，再释放节点本身

修复后代码 #

删除函数实现 #

drivers_t* node_delete(drivers_t *head, const char* target_team) {
    drivers_t *curr = head;
    drivers_t *prev = NULL;
    // 适配fgets读取内容自带换行的格式
    char team_with_newline[32] = {0};
    strcpy(team_with_newline, target_team);
    strcat(team_with_newline, "\n");

    while (curr != NULL) {
        if (strcmp(curr->team, team_with_newline) == 0) {
            // 待删节点是头节点
            if (prev == NULL) {
                head = curr->next;
            } else {
                prev->next = curr->next;
            }
            // 释放内存避免泄漏
            free(curr->name);
            free(curr->team);
            drivers_t *temp = curr;
            curr = curr->next;
            free(temp);
        } else {
            prev = curr;
            curr = curr->next;
        }
    }
    return head;
}

调用示例 #

// 加载链表
drivers_t *head = drivers_load("drivers.txt");
// 删除RedBull车队的所有车手
head = node_delete(head, "RedBull");
// 打印处理后的链表
drivers_print(head);

修正后的打印函数 #

void drivers_print(drivers_t *head){
    int number = 1;
    for (drivers_t *curr = head; curr != NULL; curr = curr->next){
        printf("%d.\n", number++);
        printf("Driver: %s", curr->name);
        printf("Team: %s", curr->team);
    }
}

修正后的加载函数 #

drivers_t *drivers_load(const char *file){
    int i = 0;
    FILE *fp = fopen(file, "r");
    if (!fp) return NULL;
    drivers_t *ptr = NULL;
    drivers_t *head = NULL;

    char buffer[255];
    while (fgets(buffer, 255, fp) != NULL){
        switch(i++){
        case 0:
            if( !ptr ) {
                ptr = drivers_new();
                head = ptr;
            }
            else {
                ptr->next = drivers_new();
                ptr = ptr->next;
            }
            break;
        case 1:
            ptr->name = strdup(buffer);
            break;
        case 2:
            ptr->team = strdup(buffer);
            i = 0;
            break;
        }
    }
    fclose(fp);
    return head;
}

内容的提问来源于stack exchange，提问作者Erri000