Question

我试图在C中实现一个简单的链接列表，但似乎没有正确添加第一个元素。这是我的代码：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>

typedef struct person{
    int phoneNumber;
    char* name;
    struct person *nextPers;
}person;

person* firstPerson=NULL;
person* lastPerson=NULL;

void addPerson (person* _person){
/*Adds a new person to the linked list after the last one added
*/  
if (firstPerson!=NULL){
    fprintf(stderr,"DEBUG(addPerson): First person is %s \n",firstPerson->name);
    fprintf(stderr,"DEBUG (addPerson): Last Person is (before adding the new one) %s \n",lastPerson->name);}
fprintf(stderr,"DEBUG: Adding person %s \n",_person->name);
_person->nextPers= NULL;
if (firstPerson==NULL){
    firstPerson = _person;
    lastPerson= _person;
    fprintf(stderr,"DEBUG: The head of the list is %s \n",firstPerson->name);   

}else{
    fprintf(stderr,"DEBUG: Last person (before adding the new one) %s \n",lastPerson->name);
    fprintf(stderr,"DEBUG (addPerson):Adding to the list %s \n",_person->name); 
    lastPerson->nextPers =_person;
    lastPerson=_person;
    fprintf(stderr,"DEBUG: Last person %s \n",lastPerson->name);
    }
}


int main(int argc, char* argv[]){
    char line[80],name[80];
    int number;
    setvbuf(stdout,(char*)malloc(sizeof(char)*80),_IOLBF,80);
    setvbuf(stdin,(char*)malloc(sizeof(char)*80),_IOLBF,80);

    for(;fgets(line,80,stdin);){
        if(!strcmp(line,"Finish\n"))
              break;

        sscanf(line,"%[^:]: %d",name,&number);
        /* Stores the person introduced from stdin as Name:phone */
        if(firstPerson!=NULL){
            fprintf(stderr,"DEBUG (Before storing new data aparently): First person is %s \n",firstPerson>name);    
        }
        person * newPerson= malloc(sizeof(person));

        newPerson->phoneNumber = number;    
        newPerson->name = name;

        fprintf(stderr,"DEBUG: Adding person %s \n",newPerson->name);
        fprintf(stderr,"DEBUG: phone number %d \n",newPerson->phoneNumber); 

        addPerson(newPerson);

        fprintf(stderr,"DEBUG: There is a new person on the list\n");                   

        }
}

预期输出为：

Harvey:12345
DEBUG: Adding person Harvey 
DEBUG: phone number 12345 
DEBUG: Adding person Harvey 
DEBUG: The head of the list is Harvey 
DEBUG: There is a new person on the list
Adam:23456 
DEBUG (Before storing new data aparently): First person is Harvey 
DEBUG: Adding person Adam 
DEBUG: phone number 23456 
DEBUG(addPerson): First person is Harvey
DEBUG (addPerson): Last Person is (before adding the new one) Harvey 
DEBUG: Adding person Adam 
DEBUG: Last person (before adding the new one) Harvey
DEBUG (addPerson):Adding to the list Adam 
DEBUG: Last person Adam  
DEBUG: There is a new person on the list

但相反，输出是：

Harvey:12345
DEBUG: Adding person Harvey 
DEBUG: phone number 12345 
DEBUG: Adding person Harvey 
DEBUG: The head of the list is Harvey 
DEBUG: There is a new person on the list
Adam:23456
DEBUG (Before storing new data aparently): First person is (null) //Wrong, its Harvey
DEBUG: Adding person Adam 
DEBUG: phone number 23456 
DEBUG(addPerson): First person is Adam //Wrong, its Harvey
DEBUG (addPerson): Last Person is (before adding the new one) Adam //Wrong, its Harvey
DEBUG: Adding person Adam 
DEBUG: Last person (before adding the new one) Adam //Wrong its Harvey
DEBUG (addPerson):Adding to the list Adam 
DEBUG: Last person Adam 
DEBUG: There is a new person on the list

总结一下，主要想法是获得一个链接列表：Harvey-＆gt; Adam-＆gt;（下一个）但我不知道错误的位置。

Answer 1

你犯了一些错误：

struct proceso *nextPers;

这没有意义，改为

person *nextPers;

然后保存在结构中的名称指向name [80]（main（）中的var），因此每次此var更改时，结构中的名称也会更改。你必须在你的结构上复制它;

memcpy(newPerson->name, name, 80);

并将结构更改为：

typedef struct person{
    int phoneNumber;
    char name[80];
    struct person *nextPers;
}person;

请记住，完成后还要清空列表中的节点

Answer 2

链接列表部分代码是正确的，这可能会让你发疯，我知道。您的代码中还有一些其他错误，与链接列表无关。

            fprintf(stderr,"DEBUG (Before storing new data aparently): First person is %s \n",firstPerson>name);

看到你写了firstPerson＆gt; name而不是firstPerson-＆gt; name，这是做一个布尔比较并返回零 - 这就是为什么你有一个＆＃34; null＆＃34;那里。

第二个错误在这里：

    newPerson->phoneNumber = number;    
    newPerson->name = name

您将phoneNumber设置为名称和数字数组的指针。所以当你在这里做第二次印刷时：

DEBUG (addPerson): Last Person is (before adding the new one) Adam //Wrong, its Harvey

它实际上正在检索正确的值 - 因为你将Harvey交给了Adam。

修复很简单：将字符串复制到newPerson中，而不是将其指向名称。

newPerson->name = malloc(sizeof(char) * strlen(name) + 1); 
strcpy(newPerson->name, name);

这应该可以解决您的问题。

在c链表中不断变化

2 个答案: