Question

strcpy strcat strcmp 函数的实现

Answer 1

void strcat(char *str1,char *str2)
{
while(*(str1++)!='\0');
str1--;
while(*str2!='\0')
*(str1++)=*(str2++);
*(str1)='\0';
}void strcpy(char *str1,char, *str2)
{
while(*(str2)!='\0')
*(str1++)=*(str2++);
*str1='\0';
}int strcmp(char *str1,char *str2)
{
while(*str1!='\0' && *str2!='\0')
{
if(*str1>*str2) return 1 ;
if(*str2<*str2) return -1;
}
return 0;
}

Answer 2

char* strcpy(char * dst, const char * src)
{
char * cp = dst;
while( *cp++ = *src++ )
; /* Copy src over dst */
return( dst );
}

char* strcat ( char * dst , const char * src )
{
char * cp = dst;
while( *cp )
cp++; /* find end of dst */
while( *cp++ = *src++ ) ; /* Copy src to end of dst */
return( dst ); /* return dst */
}

int strcmp ( const char* src, const char* dst )
{
int ret = 0 ;
while( !(ret = *(unsigned char *)src - *(unsigned char *)dst) && *dst)
++src, ++dst;
if ( ret < 0 )
ret = -1 ;
else if ( ret > 0 )
ret = 1 ;
return( ret );
}