下面这段程序大家看看有什么问题啊，小弟搞不定了。。
#include "stdio.h"
#include "string.h"
char swap(char *p1[20],char *p2[20])
{
    char *p[20];
    strcpy(p,p1);
    strcpy(p1,p2);
    strcpy(p2,p);
}
void main()
{
    char *str1[20],*str2[20],*str3[20];
    char swap();
    printf("Input three lines:\n");
    gets(str1);
    gets(str2);
    gets(str3);
    if(strcmp(str1,str2)>0) swap(str1,str2);
    if(strcmp(str1,str3)>0) swap(str1,str3);
    if(strcmp(str2,str3)>0) swap(str2,str3);
    printf("Now the order is:\n");
    printf("%s\n%s\n%s\n",str1,str2,str3);
}
下面是详细的错误信息：
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(6) : error C2664: 'strcpy' : cannot convert parameter 1 from 'char *[20]' to 'char *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(7) : error C2664: 'strcpy' : cannot convert parameter 1 from 'char *[]' to 'char *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(8) : error C2664: 'strcpy' : cannot convert parameter 1 from 'char *[]' to 'char *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(15) : error C2664: 'gets' : cannot convert parameter 1 from 'char *[20]' to 'char *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(16) : error C2664: 'gets' : cannot convert parameter 1 from 'char *[20]' to 'char *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(17) : error C2664: 'gets' : cannot convert parameter 1 from 'char *[20]' to 'char *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(18) : error C2664: 'strcmp' : cannot convert parameter 1 from 'char *[20]' to 'const char *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(18) : error C2660: 'swap' : function does not take 2 parameters
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(19) : error C2664: 'strcmp' : cannot convert parameter 1 from 'char *[20]' to 'const char *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(19) : error C2660: 'swap' : function does not take 2 parameters
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(20) : error C2664: 'strcmp' : cannot convert parameter 1 from 'char *[20]' to 'const char *'
        Types pointed to are unrelated; conversion requires reinterpret_cast, C-style cast or function-style cast
e:\program files\microsoft visual studio\myprojects\1040\1040.cpp(20) : error C2660: 'swap' : function does not take 2 parameters
执行 cl.exe 时出错.
谢谢。

#include "stdio.h"
#include "string.h"
void swap(char p1[],char p2[])  //无返回值时为：void.
{                               //参数有问题。*p1[]、*p2[]是指针数组。注意指针的用法。
    char p[20];
    strcpy(p,p1);
    strcpy(p1,p2);
    strcpy(p2,p);
}
void main()
{
    char str1[20],str2[20],str3[20];
    //char swap();
    printf("Input three lines:\n");
    gets(str1);
    gets(str2);
    gets(str3);
    if(strcmp(str1,str2)>0) swap(str1,str2);
    if(strcmp(str1,str3)>0) swap(str1,str3);
    if(strcmp(str2,str3)>0) swap(str2,str3);
    printf("Now the order is:\n");
    printf("%s\n%s\n%s\n",str1,str2,str3);
}
多练才能生巧。呵呵。加油。

[ 本帖最后由 gyx8899 于 2010-7-14 20:50 编辑 ]

多谢啊。但是我最近在练习指针的用法，用指针这个程序该怎么改呢

呃……
这用的就是指针啊……
void swap(char p1[],char p2[])  中p1[],p2[]就是指针啊。

[ 本帖最后由 gyx8899 于 2010-7-16 19:06 编辑 ]

额。char p1[],p2[];这是定义的字符数组，不是指针啊。char *p1[],*p2[]；才是定义的指针数组啊。高手指点

在形参中char p1[] 等价于 char *p1

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

int swap(char *p1,char *p2)
{
    char *p = NULL;
    p = (char *) malloc(20*sizeof(char));
    if(p == NULL)
        return (-1);
    strcpy(p,p1);
    strcpy(p1,p2);
    strcpy(p2,p);

    return (0);
}

void main()
{
    int ret = 0;
    char *str1,*str2,*str3;
    str1 = (char *)malloc(20*sizeof(char));
    if(str1 == NULL)
        return -1;
    str2 = (char *)malloc(20*sizeof(char));
    if(str2 == NULL)
        return -1;
    str3 = (char *)malloc(20*sizeof(char));
    if(str3 == NULL)   
        return -1;

    printf("Input three lines:\n");
    gets(str1);
    gets(str2);
    gets(str3);

    if(strcmp(str1,str2)>0)
        ret = swap(str1,str2);
        if(ret < 0)
            return (-1);
    if(strcmp(str1,str3)>0)
        ret = swap(str1,str3);
        if(ret < 0)
            return (-1);
    if(strcmp(str2,str3)>0)
        ret = swap(str2,str3);
        if(ret < 0 )
            return (-1);

    printf("Now the order is:\n");
    printf("%s\n%s\n%s\n",str1,str2,str3);
}
处于习惯，加了一点出错处理，看上去长了一点，其实没有变复杂。

_CRTIMP char *  __cdecl strcpy(char *, const char *);
这是vc++6.0里的关于strcpy函数的库文件
传递的是char类型的指针，并不是在你的程序里传递的char类型的指针数组的首地址

void swap(char p1[],char p2[])  中p1[],p2[]就是指针啊。
参数传递的是p1,p2.
p1,p2即指向数组的地址。

非常感谢啊，这么编问题就解决了。也谢谢楼上其他各位啊