【发布时间】：2014-03-31 18:06:52
【问题描述】：
我是 C 编程新手，我正在做一个链表，以便我可以找到、显示、 插入、删除和排序节点；但是，编译器给了我这些错误：
main.c:1:19：警告：#include 指令末尾的额外标记[默认启用]
/usr/lib/../lib64/crt1.o：在函数
_start': (.text+0x20): undefined reference tomain' collect2: error: ld 返回 1 个退出状态
我不知道它们是什么。
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
void dump_list (struct data_node *current);
void dump_node (struct data_node *current);
struct data_node * find_node (struct data_node *p, int elem);
int delete (struct data_node **p_first, int elem);
struct data_node * insert (struct data_node **p_first, int elem, char *newname);
struct data_node {
char name [25];
int data;
struct data_node *next;
};
void dump_list (struct data_node *current) {
printf("Printing list:\n");
while (current != NULL) {
printf("%s: %d\n", current->name, current->data);
current=current->next;
} /* end while */
printf("\n");
}; /* end dump_list */
void dump_node (struct data_node *current) {
printf("Printing node: ");
if (current != NULL)
printf("%s: %d\n", current->name, current->data);
}; /* end dump_node */
struct data_node * find_node (struct data_node *p, int elem) {
while (p != NULL) {
if ( elem == p->data )
return p;
p=p->next;
} /* end while */
if(p==NULL){
printf("Node not found\n");
return p;
}
}; /* end find_node */
int delete (struct data_node **p_first, int elem) {
int retval = 0;
struct data_node *current, *prev;
current=*p_first;
while (current != NULL && elem != current->data ) {
prev=current;
current=current->next;
}
if (current == NULL) /* element not found */
return retval;
/* current now points to node to delete */
if ( current == *p_first ) /* delete 1st node */
*p_first = (*p_first)->next;
else /* link previous to next thus skipping over node to delete */
prev->next=current->next;
free(current);
retval=1;
return retval;
}; /* end delete */
struct data_node * insert (struct data_node **p_first, int elem, char *newname) {
struct data_node *new_node, *prev, *current;
current=*p_first;
while (current != NULL && elem > current->data) {
prev=current;
current=current->next;
} /* end while */
/* current now points to position *before* which we need to insert */
new_node = (struct data_node *) malloc(sizeof(struct data_node));
new_node->data=elem;
strcpy(new_node->name, newname);
new_node->next=current;
if ( current == *p_first ) /* insert before 1st element */
*p_first=new_node;
else /* now insert before current */
prev->next=new_node;
/* end if current == *p_first */
return new_node;
}; /* end insert */
int main (void) {
char key;
int newelem;
char newstring [25];
int removeelem;
int findelem;
struct data_node *first=NULL, *ptr;
printf ("Enter list command (+-flx): ");
scanf (" %c", &key);
int newelem;
char newstring [25];
int removeelem;
int findelem;
switch (key)
{
/* tyep +*/
case '+':
printf ("+ detected \n");
printf ("Enter key data: \n");
scanf ("%D", &newelem);
printf ("What string to store? \n");
gets(newstring);
insert(&first, newelem,newstring);
break;
/* tyep -*/
case '-':
printf ("- detected \n");
printf ("Enter key data: \n");
scanf ("%D", &removeelem);
delete(&first, removeelem);
if(delete(&first, removeelem) ==0)
printf ("Data not found. No deletion performed. \n");
break;
/* tyep f*/
case 'f':
printf ("f detected \n");
printf ("Enter key data: \n");
scanf ("%D", &findelem);
while (ptr != NULL)
{
ptr=find_node(first, findelem);
dump_node(ptr);
}
printf ("Node not found. \n");
break;
/* tyep l*/
case 'l':
printf ("l detected \n");
dump_list(first);
break;
/* tyep x*/
case 'x':
printf ("Goodbye. \n");
break;
/* no default case necessary here */
}
return (0);
} /* end main */
【问题讨论】：
-
你为什么重复你的#includes和你对data_node的定义？
-
不要在 Web 端向我们发送您的整个代码，而是将其简化为重现您的问题的最小示例。通过这样做，您可能会自己发现错误。很可能这甚至不是产生错误的代码，而是您混淆了文件。
-
"main.c:1:19: 警告：#include 指令末尾的额外标记" 暗示这是第 19 行末尾的内容：可能是
#include <stdlib.h>。它可以是像'\r'这样的空格。有时这发生在混合编辑器中。如果需要，删除第 19 行并重新输入。
标签： c pointers struct linked-list