自己写一个strcmp函数。结果不太正确。

[一起来C吧]

#include<stdio.h>

strcmp(char *p1,char *p2)
{
int i=0;
while(*(p1+i++)==*(p2+i++))
return (*(p1+i)-*(p2+i));

}

int main()
{
int m;
char str1[20],str2[20],*p1,*p2;
printf("input two stings:\n");
scanf("%s",str1);
scanf("%s",str2);
p1=&str1[0];
p2=&str2[0];
m=strcmp(p1,p2);
printf("result:%d\n",m);
return 0;
}
如题。当输入两个都是单个字符比较时。好像返回的值不正确。请指点一下。程序哪里有问题。谢谢

[hrx1989]

strcmp就错了吧。

[LinuxBirdMan]

int strcmp(char *p1,char *p2)
{
	if(!p1 || !p2)
	{
		printf("illeg pointer\n");
		exit(0);
	}

	while(*(p1)!= '\0' && *(p2)!= '\0')
	{
		if(*p1!=*p2)
			return ((*p1)-(*p2));
		else
		{
			p1++;
			p2++;
			continue;
		}
	}
	if(*p1== '\0' && *p2=='\0')
		return 0;
	else
		return ((*p1)-(*p2));
}

[sxqinge]

void strcpy(char* Dest, char* Src)
{
  ASSERT((Dest != NULL) && (Src != NULL) );
  while( *Src != '\0' && *Dest != '\0' )
  {
    *Dest++ = *Src++;
  }
}

[sxqinge]

啊，没看清楼主的问题，我以为是COPY呢！

[sxqinge]

int strcmp(char* str1, char* str2)
{
  ASSERT( ( str1 != NULL ) && ( str2 != NULL ) );
  if ( *str1 != *str2 )
    return ( (*str1) - (*str2) );
  else
  {
    if ( *str1 == '\0' && *str2 == '\0' )
      return 0;
    else
      return strcmp( str1+1, str2+1 );
  }      
}

[庄鱼]

[Quote=引用楼主 yuyan_c 的回复:]
#include<stdio.h>

strcmp(char *p1,char *p2)
{
int i=0;
while(*(p1+i++)==*(p2+i++))
return (*(p1+i)-*(p2+i));

}

int main()
{
int m;
char str1[20],str2[20],*p1,*p2;
printf("input two st……
[/Quote]
while(*(p1+i)== *(p2+i))i++;

[eternalxlm]

[Quote=引用楼主 yuyan_c 的回复:]

while(*(p1+i++)==*(p2+i++))
return (*(p1+i)-*(p2+i));

[/Quote]

你的return在while循环里，所以按你的程序只要前2个字母一样就会返回0。
单字符的字符串你都会返回0，因为你return的是'\0'-'\0'。

[crjwlaq]

你那返回的差值是 anscii码的差值

[crjwlaq]

[Quote=引用 12 楼 freefice 的回复:]

引用楼主 yuyan_c 的回复:
#include<stdio.h>

strcmp(char *p1,char *p2)
{
int i=0;
while(*(p1+i++)==*(p2+i++))
return (*(p1+i)-*(p2+i));

}

int main()
{
int m;
char str1[20],str2[20],*p1,*p2;
……
[/Quote]

这个补充的不错

[兴文哥]

#include <stdio.h>
int strcmp(char *p1,char *p2)
{
while(*p1++=*p2++);
return *p1-*p2;
}

[兴文哥]

哦，错老，不好意思！
#include <stdio.h>
int strcmp(char *p1,char *p2)
{
while(*p1++==*p2++);
return *p1-*p2;
}

[masmaster]

这是我编写的比较两个字串练习（还没有学到指针）。

int cmpstr (char s1[],char s2[]) {
        int i=0;
        while(s1[i]!='\0'&&s2[i]!='\0') {
                if(s1[i]>s2[i]) {
                        return 1;
                }
                if(s1[i]<s2[i]) {
                        return -1;
                }
                i++;
        }
        if(s1[i]=='\0'&&s2[i]=='\0') {
                return 0;
        }
}

[nanbazhangbiao]

楼主，你这是在考研编译器。。不同的编译器，结果会不同的。
while(*(p1+i++)==*(p2+i++))
对于p1+i++，编译器处理不一样

[quwei197874]

用unsigned转换后再比较.

[ufozhoujie]

LZ啊，我不得不批评你了····这写得什么哟！
第一有明显的语法错误；
第二貌似逻辑不够清晰；
第三编程不规范额···对于自增的处理，你的确是在考验编译器！

[碎碎念]

strcmp(char *p1,char *p2)
{
int i=0;
while(*(p1+i++)==*(p2+i++))
return (*(p1+i)-*(p2+i));

}
lz这样写...strcmp返回值类型都没写- -

我也写个...
int strcmp(char* p1,char* p2)
{
if(strlen(p1)!=strlen(p2))
return 0;
int len=strlen(p1);
int rst;
for(int i=0;i<len;i++)
{
if(p1[i]!=p2[i])
{
rst=0;
break;
}
else
rst=1;
}
return rst;
}

[AnYidan]

while(*(p1+i++)==*(p2+i++)) // 假设此时 i = 5
return (*(p1+i)-*(p2+i)); // 此时 i = 6

是你的意思吗？

[Roy_Smiling]

[Quote=引用 2 楼 linuxbirdman 的回复:]

C/C++ code
int strcmp(char *p1,char *p2)
{
if(!p1 || !p2)
{
printf("illeg pointer\n");
exit(0);
}

while(*(p1)!= '\0' && *(p2)!= '\0')
{
if(*p1!=*……
[/Quote]

done a good job!

[emailtome]

我贴个现成的别BS我

/* Copyright (C) 1991, 1996, 1997, 2003 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, write to the Free
   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
   02111-1307 USA.  */

#include <string.h>
#include <memcopy.h>

#undef strcmp

/* Compare S1 and S2, returning less than, equal to or
   greater than zero if S1 is lexicographically less than,
   equal to or greater than S2.  */
int
strcmp (p1, p2)
     const char *p1;
     const char *p2;
{
  register const unsigned char *s1 = (const unsigned char *) p1;
  register const unsigned char *s2 = (const unsigned char *) p2;
  unsigned reg_char c1, c2;

  do
    {
      c1 = (unsigned char) *s1++;
      c2 = (unsigned char) *s2++;
      if (c1 == '\0')
        return c1 - c2;
    }
  while (c1 == c2);

  return c1 - c2;
}
libc_hidden_builtin_def (strcmp)