c - 字符串数组和 Gnome 排序

Question

任务:我正在开发一个程序，该程序应使用 gnome 排序对字符串数组进行排序(rosettacode.com 上提供了相关代码)

问题:编译代码后，没有报错，但是当我执行程序时，打印出未排序的数组，并且出现“segmentation fault(core dumped)”错误:

____( 6:46PM)[Sergiy@Ubuntu]:_____ ~> ./a.out

Unsorted: state 0: California state 1: Oregon state 2: Washington state 3: Texas zsh: segmentation fault (core dumped) ./a.out

我无法弄清楚问题出在哪里。排序功能肯定有问题，只是无法弄清楚到底是什么。

源代码:

#include<stdio.h>
#include<string.h>


void
gnome_sort (char *a[], int n)
{
  int i = 1, j = 2;
  char temp[20];


//#define swap(i, j) { t = a[i]; a[i] = a[j]; a[j] = t; } 
  while (i < n)
    {
      if (strcmp (a[n - 1], a[n]) > 0)
    {
      //swap(i - 1, i);
      strcpy (temp, a[i]);
      strcpy (a[i], a[i - 1]);
      strcpy (a[i - 1], temp);
      if (--i)
        continue;
    }

      i = j;
      j++;



    }
//# undef swap
}


int
main ()
{

  char *states[] = { "California", "Oregon", "Washington", "Texas" };
  int num_states = 4;

 // int n;

//n=sizeof a / sizeof a[0];

//printf("n is %d ",n);

  int i;
  printf ("\n Unsorted:\n");

  for (i = 0; i < num_states; i++)
    {
      printf ("state %d: %s\n", i, states[i]);
    }

  gnome_sort (states,num_states);

  printf ("\n Sorted: \n");

  for (i = 0; i < num_states; i++)
    {
      printf ("state %d: %s\n", i, states[i]);
    }


  return 0;
}

更新:所以我找到了一种使程序运行的方法。正如这里的用户正确提到的那样，我必须使传递的字符串都具有相同的大小，并使用 this post here 实现了这一点。但是当程序进入排序功能时，我仍然遇到问题。

更新代码 1 #include 2 #include

 3  void
 4  gnome_sort (char states[][20], int n)
 5  {

 6    int i = 0, j = 2;
 7    char temp[20];


 8    while (i < n)
 9      {

10        printf ("\n *** Inside while loop *** \n");
11        printf ("\n %d", strcmp (states[i - 1], states[i]));
12        if (strcmp (states[i - 1], states[i]) < 0)
13      {

14        strcpy (temp, states[i]);
15        printf ("\n %s \n", temp);
16        strcpy (states[i], states[i - 1]);
17        strcpy (states[i - 1], temp);
18        if (--i)
19          continue;
20      }

21        i = j;
22        j++;



23      }


24    printf ("\n Sorted in gnome sort: \n");

25    for (i = 0; i < n; i++)
26      {
27        printf ("state %d: %s\n", i, states[i]);
28      }



29  //end of function
30  }


31  int
32  main ()
33  {

34    char states[][20] = { "Washington", "Colorado", "Iowa", "Texas" };
35    int num_states = 4;

36    // int n;

37  //n=sizeof a / sizeof a[0];

38  //printf("n is %d ",n);

39    int i;
40    printf ("\n Unsorted:\n");

41    for (i = 0; i < num_states; i++)
42      {
43        printf ("state %d: %s\n", i, states[i]);
44      }

45    gnome_sort (states,num_states);

46  /*  printf ("\n Sorted: \n");

47    for (i = 0; i < num_states; i++)
48      {
49        printf ("state %d: %s\n", i, states[i]);
50      }*/


51    return 0;
52  }

更新后的输出:

$ ./a.out

 Unsorted:
state 0: Washington
state 1: Colorado
state 2: Iowa
state 3: Texas

 *** Inside while loop *** 

 -87
 Washington 

 *** Inside while loop *** 

 -87
 Washington 

 *** Inside while loop *** 

 18
 *** Inside while loop *** 

 -6
 Iowa 

 *** Inside while loop *** 

 -73
 Iowa 

 *** Inside while loop *** 

 -17
 Texas 

 *** Inside while loop *** 

 -84
 Texas 

 *** Inside while loop *** 

 -11
 Texas 

 Sorted in gnome sort: 
state 0: Texas
state 1: Iowa
state 2: 
state 3: Colorado
*** stack smashing detected ***: ./a.out terminated
Aborted (core dumped) 

最终解决方案: 堆栈粉碎可能是因为字符串大小不够大，我有点被另一个 stackoverflow post 暗示了。该程序现在可以像我想要的那样工作，但不知道为什么字符串必须是 30 个字符长，因为最大的字符串 - Washington - 是 10 个字符长，远低于 20 个字符。

最终代码:

1   #include<stdio.h>
     2  #include<string.h>

     3  void
     4  gnome_sort (char states[][30], int n)
     5  {

     6    int i = 1, j = 2;
     7    char temp[30];


     8    while (i < n)
     9      {

    10        printf ("\n *** Inside while loop *** \n");
    11        printf ("\n %d", strcmp (states[i - 1], states[i]));
    12        if (strcmp (states[i - 1], states[i]) > 0)
    13      {

    14        strcpy (temp, states[i]);
    15        printf ("\n %s \n", temp);
    16        strcpy (states[i], states[i - 1]);
    17        strcpy (states[i - 1], temp);
    18        if (--i)
    19          continue;
    20      }

    21        i = j;
    22        j++;



    23      }


    24    printf ("\n Sorted in gnome sort: \n");

    25    for (i = 0; i < n; i++)
    26      {
    27        printf ("state %d: %s\n", i, states[i]);
    28      }



    29  //end of function
    30  }


    31  int
    32  main ()
    33  {

    34    char states[][30] = { "Washington", "Colorado", "Iowa", "Texas" };
    35    int num_states = 4;

    36    // int n;

    37  //n=sizeof a / sizeof a[0];

    38  //printf("n is %d ",n);

    39    int i;
    40    printf ("\n Unsorted:\n");

    41    for (i = 0; i < num_states; i++)
    42      {
    43        printf ("state %d: %s\n", i, states[i]);
    44      }

    45    gnome_sort (states,num_states);

    46  /*  printf ("\n Sorted: \n");

    47    for (i = 0; i < num_states; i++)
    48      {
    49        printf ("state %d: %s\n", i, states[i]);
    50      }*/


    51    return 0;
    52  }

最终输出:

$ ./a.out

 Unsorted:
state 0: Washington
state 1: Colorado
state 2: Iowa
state 3: Texas

 *** Inside while loop *** 

 20
 Colorado 

 *** Inside while loop *** 

 14
 Iowa 

 *** Inside while loop *** 

 -6
 *** Inside while loop *** 

 3
 Texas 

 *** Inside while loop *** 

 -11
 Sorted in gnome sort: 
state 0: Colorado
state 1: Iowa
state 2: Texas
state 3: Washington

Answer 1

您的排序代码在 a(最初是 states)的元素之间复制字符串，但并非所有这些字符串的大小都相同。因此，如果您要将某些内容复制到 Texas 所在的位置，则副本将越过 Texas 结束的位置，从而修改 Texas 之后存储在空间中的任何内容。