我正在尝试使用 strcmp() 对 C 中的字符串数组进行排序

Question

我有一个让我头疼的家庭作业挑战。问题是：

构建一个使用字符串数组存储以下名称的程序：
*“佛罗里达”
*“俄勒冈”
*“加利福尼亚”
*“格鲁吉亚”
使用前面的字符串数组，编写您自己的 sort() 函数，使用 strcmp() 函数按字母顺序显示每个州的名称。

这是给我带来问题的代码：

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

//function prototype
int sort(char *, char *);

int main() 
{
    char *strStates[] = {"Florida", "Oregon", "California", "Georgia"};
    char *strSorted[] = {0};
    int x;

    printf("\nThe list of states before being sorted in alphabetical order: ");

    for (x = 0; x < 4; x++) 
    {
        printf("\n%s", strStates[x]);
    }

    sort(strStates[x], strSorted[x]);

    printf("\nThe list of states sorted alphabetically are: ");

    for (x = 0; x < 4; x++) 
    {
        printf("\n%s", strStates[x]);
    }

    return 0;

}//end main

//function definition
int sort(char *string1, char *string2)
{
    int x;
    int y;

    for (x = 0; x < 3; x++) 
    {
        for (y = 1; y < 4; y++) 
        {
            if ((strcmp(string1[x], string1[y])) > 0) 
            {
                strcpy(string2, string1[x]);
                strcpy(string1[x], string1[y]);
                strcpy(string[y], string2);
            }//end if

       }//end inner for loop

    }//end outer for loop

}//end sort()

我在编译时遇到了一系列错误：

Chapter_8_Challenge_3.c:45:16: warning: incompatible integer to pointer conversion passing 'char' to parameter of type 'const char *'; take the address with & [-Wint-conversion]
                    if ((strcmp(string1[x], string1[y])) > 0) 
                                ^~~~~~~~~~
                                &  
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/string.h:77:25: note: passing argument to parameter here
int      strcmp(const char *, const char *);
                        ^  
Chapter_8_Challenge_3.c:45:28: warning: incompatible integer to pointer conversion passing 'char' to parameter of type 'const char *'; take the address with & [-Wint-conversion]
                    if ((strcmp(string1[x], string1[y])) > 0) 
                                            ^~~~~~~~~~
                                            &  
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/string.h:77:39: note: passing argument to parameter here
int      strcmp(const char *, const char *);
                                      ^  
Chapter_8_Challenge_3.c:47:21: warning: incompatible integer to pointer conversion passing 'char' to parameter of type 'const char *'; take the address with & [-Wint-conversion]
                            strcpy(string2, string1[x]);
                                            ^~~~~~~~~~
                                            &  
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/secure/_string.h:83:33: note: expanded from macro 'strcpy'
  __builtin___strcpy_chk (dest, src, __darwin_obsz (dest))
                            ^  
Chapter_8_Challenge_3.c:48:12: warning: incompatible integer to pointer conversion passing 'char' to parameter of type 'const void *' [-Wint-conversion]
                            strcpy(string1[x], string1[y]);
                                   ^~~~~~~~~~  
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/secure/_string.h:83:53: note: expanded from macro 'strcpy'
  __builtin___strcpy_chk (dest, src, __darwin_obsz (dest))
                                                ^  
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/secure/_common.h:39:54: note: expanded from macro '__darwin_obsz'
#define __darwin_obsz(object) __builtin_object_size (object, _USE_FORTIFY_LEVEL > 1 ? 1 : 0)
                                                 ^  
Chapter_8_Challenge_3.c:48:12: warning: incompatible integer to pointer conversion passing 'char' to parameter of type 'char *'; take the address with & [-Wint-conversion]
                            strcpy(string1[x], string1[y]);
                                   ^~~~~~~~~~
                                   &  
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/secure/_string.h:83:27: note: expanded from macro 'strcpy'
  __builtin___strcpy_chk (dest, src, __darwin_obsz (dest))
                      ^  
Chapter_8_Challenge_3.c:48:24: warning: incompatible integer to pointer conversion passing 'char' to parameter of type 'const char *'; take the address with & [-Wint-conversion]
                            strcpy(string1[x], string1[y]);
                                               ^~~~~~~~~~
                                               &  
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/secure/_string.h:83:33: note: expanded from macro 'strcpy'
  __builtin___strcpy_chk (dest, src, __darwin_obsz (dest))
                            ^  
Chapter_8_Challenge_3.c:49:12: error: use of undeclared identifier 'string'; did you mean 'string1'?
                            strcpy(string[y], string2);
                                   ^~~~~~
                                   string1  
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/secure/_string.h:83:27: note: expanded from macro 'strcpy'
  __builtin___strcpy_chk (dest, src, __darwin_obsz (dest))
                      ^  
Chapter_8_Challenge_3.c:36:16: note: 'string1' declared here
int sort(char *string1, char *string2)
           ^  
Chapter_8_Challenge_3.c:49:12: error: use of undeclared identifier 'string'
                            strcpy(string[y], string2);
                                   ^  
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/secure/_string.h:83:53: note: expanded from macro 'strcpy'
  __builtin___strcpy_chk (dest, src, __darwin_obsz (dest))
                                                ^  
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/secure/_common.h:39:54: note: expanded from macro '__darwin_obsz'
#define __darwin_obsz(object) __builtin_object_size (object, _USE_FORTIFY_LEVEL > 1 ? 1 : 0)  
                                                 ^
6 warnings and 2 errors generated.

Answer 1

1. 在你的函数sort -

if((strcmp(string1[x],string1[y]))>0) //string1[x] is of type char-Wrong argument to strcmp 
        {
            strcpy(string2, string1[x]);          // same problem as aboce for all 
            strcpy(string1[x], string1[y]);
            strcpy(string[y], string2);
        }//end if 

这个 string1 已经是 char * 并且 string1[x] 将是 char 类型。所以这会调用未定义的行为。

2. 在main -

 for (x = 0; x < 4; x++) 
{
    printf("\n%s", strStates[x]);
}

sort(strStates[x], strSorted[x]);

也许您打算将 char 指针数组 (strStates) 作为第一个参数，将 (strSorted) 作为第二个参数。那么上面sort中的问题也就解决了。

3. 最后你运行int sort() 没有return 任何东西，所以你又得到了自己UB。

注意 - 您得到的错误是因为将 char 传递给字符串函数。

Answer 2

除了sort 函数参数的错误之外，您还应该考虑使用strcpy。您不能将一个字符串文字复制到另一个字符串文字中，因为它们是只读的。

你真的需要复制字符串吗？您输入了指向字符串的指针数组。您可以只对那些指针进行排序，而无需触及实际的字符串。

您可以只传递该指针数组并对其进行排序：

void sort(char *strStates[])
{
    int x, y;

    for (x = 0; x < 3; x++) 
    {
        for (y = x + 1; y < 4; y++)
        {
            if ((strcmp(strStates[x], strStates[y])) > 0) 
            {
                char *tmp = strStates[x];
                strStates[x] = strStates[y];
                strStates[y] = tmp;
            }//end if
       }//end inner for loop
    }//end outer for loop
}//end sort()

可以叫sort(strStates)。

您还可以考虑将数组大小传递给该函数以避免幻数3 和4：void sort(char *strStates[], int size)。

Answer 3

您的 sort 函数接收 2 个字符串作为参数，因此 if ((strcmp(string1[x], string1[y])) > 0) 正在尝试将两个字符与 strcmp 进行比较。你的排序函数应该更像这样：

void sort(char **unsortedStrings){
    int x;
    int y;
    for (x = 0; x < 3; x++) 
    {
        for (y = x+1; y < 4; y++) 
        {
            if ((strcmp(unsortedStrings[x], unsortedStrings[y])) > 0) 
            {
                // There is no need to use strcpy here, just re-order the pointers
                char *tmp = unsortedStrings[x];
                unsortedStrings[x] = unsortedStrings[y];
                unsortedStrings[y] = tmp;
            }//end if

      }//end inner for loop

   }//end outer for loop
}//end sort()

此外，您的排序函数说它应该返回一个 int，但没有返回任何内容。要么你返回一些东西（比如return 1，如果一切正常，或者return 0，如果失败）或者你应该将它声明为void