Question

我需要一些关于此链接列表练习的帮助。函数listTasks()应该显示struct task的所有实例。当我第一次执行该函数时，它按预期工作，但是当我再次执行它时，它不会显示来自struct action的内容，即使我依次执行它们。

typedef struct action
{
    char parametre[100];
    char command[100];
    struct action* next;
    struct action* previous;
}* Action;

typedef struct task
{
    char name[100];
    struct task* next;
    struct task* previous;
    Action action;
}* Task;

void listTasks(Task tar, char* name)
{

    if(tar==NULL) printf("There is no task with the name: %s\n",name);
    else
    {
        while(tar!=NULL&&strcmp(tar->name,name)!=0)
        {
            tar = tar->next;
        }
        if(tar!=NULL && strcmp(tar->name,name)==0)
        {
            printf("Task: %s\n",tar->name);
            if(tar->action==NULL) printf("->It doesnt have any action.\n");
            else if(tar->action!=NULL)
            {
                while(tar->action!=NULL)
                {
                    printf("->Command: %s\n->->Parametre: %s\n",tar->action->command,tar->action->parametre);
                    tar->action = tar->action->next;
                }
            }
        }
        else printf("There is no task with the name: %s\n",name);
    }


}

void main()
{
   task a = NULL;
   listTasks(a,"random name");
}

Answer 1

你的问题在这里：

while(tar->action!=NULL)
{
    printf("->Command: %s\n->->Parametre: %s\n",tar->action->command,tar->action->parametre);
    tar->action = tar->action->next;
}

你正在破坏性地改变tar->action。是的，它第一次有效，但在此之后，tar->action将是NULL，这就是数据“消失”的原因。

如果您不想销毁操作列表，则必须使用临时变量遍历它。有点像：

struct action *action = tar->action;
while(action!=NULL)
{
    printf("->Command: %s\n->->Parametre: %s\n",action->command,action->parametre);
    action = action->next;
}

链接列表 - 数据消失

1 个答案: