c - 我的实现未能删除 c 中 String 的最后一个字符

Question

这是我定义的LinkedList:

typedef struct target{
  char my_target[65];
  int ID;
  struct target *next;
}target_list;

这是一个有效的解决方案:

printf("the last node is %s\n",get_nth(&head,target_id));
if (get_nth(&head,target_id)[strlen(get_nth(&head,target_id))-1] == '\n'){
  char *p = get_nth(&head,target_id);
  p[strlen(get_nth(&head,target_id))-1] = 0;
  //change_nth(&head,target_id);
  printf("the copied array is %s\n",p);

}

打印结果如下:

the last node is Git

the copied array is Git

但是我想更改链表中的第n个节点，如下所示:我定义了两个辅助方法，一个用于获取第n个节点，一个用于删除第n个节点的字符数组中的'\n'。

char* get_nth(target_list* head, int index)
{
  target_list* current = head;
  int cnt = 0;
  while(current != NULL){
    if (cnt == index)
      return(current -> my_target);
  cnt++;
  current = current -> next;
}
  return "";
}

void change_nth(target_list* head, int index)
{
  target_list* current = head;
  int cnt = 0;
  while(current != NULL){
    if (cnt == index){
      char *p = current -> my_target;
      p[strlen(current -> my_target)-1] = 0;
      strcpy(current -> my_target,"");
      strcpy(current -> my_target,p);

    }
  cnt++;
  current = current -> next;
}
}

这是更改后的主要内容:

printf("the last node is %s\n",get_nth(&head,target_id));
    if (get_nth(&head,target_id)[strlen(get_nth(&head,target_id))-1] == '\n'){
      //char *p = get_nth(&head,target_id);
      //p[strlen(get_nth(&head,target_id))-1] = 0;
      change_nth(&head,target_id);
      printf("the copied array is %s\n",get_nth(&head,target_id));

    }

这里出现错误:

the last node is Git

==25553== Source and destination overlap in strcpy(0x5201470, 0x5201470)
==25553==    at 0x4C2E272: strcpy (in *)
==25553==    by 0x40120F: change_nth (original.c:213)
==25553==    by 0x4015D6: main (original.c:318)
==25553== 
the copied array is 

C 字符串让我困惑了很长时间，任何帮助将不胜感激!

Answer 1

这里有一些功能

char *removelast(char *str)
{
    size_t len;
    if(str == NULL) return NULL;
    if(!(len = strlen(str))) return str;
    str[len - 1] = 0;
    return str;
}

char *removenth(char *str, size_t nth) // nth - 0 to strlen - 1
{
    size_t len;
    if(str == NULL) return NULL;
    if(!(len = strlen(str)) || nth >= len) return str;
    strcpy(&str[nth], &str[nth + 1]);
    return str;
}


int main(void) {
    char str[] = "Hello stackoverflow!!";
    printf("Original      - %s\n", str);
    printf("Last removed  - %s\n", removelast(str));
    printf("Third removed - %s\n", removenth(str,2)); // third means 2
    return 0;
}

你可以在这里自己玩一下https://ideone.com/Vnkzjp

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