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这个链表小程序用子函数表述为什么不成

发布时间： 2013-08-13 16:43:28 作者： rapoo

这个链表小程序用子函数表达为什么不成功？
我先在main函数里建立了链表，然后尝试用子函数来编写，总是不成功。一定在错误，不知怎么改？请指点。
下面是在main中建立链表的程序：

#include "stdafx.h"
#include "stdio.h"
#include "string.h"
#include "stdbool.h"
#include "stdlib.h"

#define SIZE 40

struct film
{
char title[SIZE];
int rating;
};

typedef struct film Item;

typedef struct node
{
Item item;
struct node * next;
}Node;

int main(void)
{
Node *head = NULL, *current, *prev;
Item item;

puts("Enter first movie");
while(gets(item.title)!=NULL && item.title[0]!='\0')
{

puts("Enter the rating <0-10>:");
scanf("%d", &item.rating);
while(getchar() != '\n')
{
continue;
}

current = (Node *)malloc(sizeof(Node));
if(head == NULL)
{
head = current;
}
else
{
prev->next = current;
}
current->item = item;
current->next = NULL;
prev = current;
puts("Enter another movie:");
}

current = head;
while(current != NULL)
{
printf("%s %d\n", current->item.title, current->item.rating);
current = current->next;
}
putchar('\n');
return 0;
}


下面是我想在子函数中编写一部分，但是不成功

#include "stdafx.h"
#include "stdio.h"
#include "string.h"
#include "stdbool.h"
#include "stdlib.h"

#define SIZE 40

struct film
{
char title[SIZE];
int rating;
};

typedef struct film Item;

typedef struct node
{
Item item;
struct node * next;
}Node;

Node * CreateList(Item item);

int main(void)
{
Node *head = NULL, *current;
Item item;

puts("Enter first movie");
while(gets(item.title)!=NULL && item.title[0]!='\0')
{

puts("Enter the rating <0-10>:");
scanf("%d", &item.rating);
while(getchar() != '\n')
{
continue;
}
head = CreateList(item);
puts("Enter another movie:");
}

current = head;
while(current != NULL)
{
printf("%s %d\n", current->item.title, current->item.rating); 
 
current = current->next;
}
putchar('\n');
return 0;
}

Node * CreateList(Item item)
{
Node *head, *current, *prev;
current = (Node *)malloc(sizeof(Node));
current->item = item;
current->next = NULL;
if(head == NULL)
{
head = current;
}
else
{
prev->next = current;
}
prev = current;

return head;
}

[解决办法]

  Node * CreateList(Item item)
{
   // Node *head, *current, *prev; //这个时候是野指针哦！不是为NULL的
    Node *head = NULL;
    Node *current = NULL;
    Node *prev = NULL;
    current = (Node *)malloc(sizeof(Node));
    current->item = item;
    current->next = NULL;
    if(head == NULL)
    {
        head = current;   
    }
    else
    {
        prev->next = current;
    }   
    prev = current;
 
    return head;
}


[解决办法]


  Node * CreateList(Item item)
{
    static Node *head = NULL;
    static Node *current = NULL;
    static Node *prev = NULL;
    current = (Node *)malloc(sizeof(Node));
    current->item = item;
    current->next = NULL;
    if(head == NULL)
    { 
 
        head = current;   
    }
    else
    {
        prev->next = current;
    }   
    prev = current;
 
    return head;
}

[解决办法]
Node * CreateList(Item item)
{
   // Node *head, *current, *prev;
    Node *head = NULL;
    Node *current = NULL;
    Node *prev = NULL;
    current = (Node *)malloc(sizeof(Node));
    current->item = item;
    current->next = NULL;
    if(head == NULL)
    {
        head = current;   
    }
    else
    {
        prev->next = current;
    }   
    prev = current;
    current = (Node *)malloc(sizeof(Node));
    return head;
}

[解决办法]
引用:
我先在main函数里建立了链表，然后尝试用子函数来编写，总是不成功。一定在错误，不知怎么改？请指点。
下面是在main中建立链表的程序：

#include "stdafx.h"
#include "stdio.h"
#include "string.h"
#include "stdbool.h"
#include "stdlib.h"

#define SIZE 40

struct film
{
char title[SIZE];
int rating;
};

typedef struct film Item;

typedef struct node
{
Item item;
struct node * next;
}Node;

int main(void)
{
Node *head = NULL, *current, *prev;
Item item;

puts("Enter first movie");
while(gets(item.title)!=NULL && item.title[0]!='\0')
{

puts("Enter the rating <0-10>:");
scanf("%d", &item.rating);
while(getchar() != '\n')
{
continue;
}

current = (Node *)malloc(sizeof(Node));
if(head == NULL) 
 
{
head = current;
}
else
{
prev->next = current;
}
current->item = item;
current->next = NULL;
prev = current;
puts("Enter another movie:");
}

current = head;
while(current != NULL)
{
printf("%s %d\n", current->item.title, current->item.rating);
current = current->next;
}
putchar('\n');
return 0;
}


下面是我想在子函数中编写一部分，但是不成功

#include "stdafx.h"
#include "stdio.h"
#include "string.h"
#include "stdbool.h"
#include "stdlib.h"

#define SIZE 40

struct film
{
char title[SIZE];
int rating;
};

typedef struct film Item;

typedef struct node
{
Item item;
struct node * next;
}Node;

Node * CreateList(Item item);

int main(void)
{
Node *head = NULL, *current;
Item item;

puts("Enter first movie");
while(gets(item.title)!=NULL && item.title[0]!='\0')
{

puts("Enter the rating <0-10>:");
scanf("%d", &item.rating);
while(getchar() != '\n')
{
continue;
}
head = CreateList(item);
puts("Enter another movie:");
}

current = head;
while(current != NULL)
{
printf("%s %d\n", current->item.title, current->item.rating);
current = current->next;
}
putchar('\n');
return 0;
}

Node * CreateList(Item item)
{
Node *head, *current, *prev;
current = (Node *)malloc(sizeof(Node));
current->item = item;
current->next = NULL;
if(head == NULL)
{
head = current;
}
else
{
prev->next = current;
}
prev = current;

return head;
}


在createlist函数中，每次都会将head设置为NULL,所以只会执行if判断中的 head = current;
然后返回head，所以每次你的程序只会记录最后一个节点的值。
在这种情况下，最好是将head变量设置成全局的，还有就是你的prev变量需要设置成静态的，否则，
在每次执行createlist函数的时候，首先会将其设置为NULL，然后执行else中的 prev->next = current;
这也是不对的，因为当前的prev的值为NULL，这样做的话会发生段错误。
骚年，建议你重新考虑下你的代码设计，或者去看看别人是怎么实现的

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