/***

*char *strcpy(dst, src) - copy one string over another

*

*Purpose:

* Copies the string src into the spot specified by

* dest; assumes enough room.

*

*Entry:

* char * dst - string over which "src" is to be copied

* const char * src - string to be copied over "dst"

*

*Exit:

* The address of "dst"

*

*Exceptions:

*******************************************************************************/

char* strcpy(char * dst, const char * src)

{

char * cp = dst;

while( *cp++ = *src++ )

; /* Copy src over dst */

return( dst );

}

/***

*char *strcat(dst, src) - concatenate (append) one string to another

*

*Purpose:

* Concatenates src onto the end of dest. Assumes enough

* space in dest.

*

*Entry:

* char *dst - string to which "src" is to be appended

* const char *src - string to be appended to the end of "dst"

*

*Exit:

* The address of "dst"

*

*Exceptions:

*

*******************************************************************************/

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 */

}

/***

*strcmp - compare two strings, returning less than, equal to, or greater than

*

*Purpose:

* STRCMP compares two strings and returns an integer

* to indicate whether the first is less than the second, the two are

* equal, or whether the first is greater than the second.

*

* Comparison is done byte by byte on an UNSIGNED basis, which is to

* say that Null (0) is less than any other character (1-255).

*

*Entry:

* const char * src - string for left-hand side of comparison

* const char * dst - string for right-hand side of comparison

*

*Exit:

* returns -1 if src < dst

* returns 0 if src == dst

* returns +1 if src > dst

*

*Exceptions:

*

*******************************************************************************/

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 );

}

 itoa atoi

[csharp]  view plain copy
  1. void itoa(int num,char str[] )  
  2. {  
  3.     int sign = num,i = 0,j = 0;  
  4.     char temp[11];  
  5.       
  6.     if(sign<0)//判断是否是一个负数  
  7.     {  
  8.         num = -num;  
  9.     }  
  10.       
  11.     do  
  12.     {  
  13.         temp[i] = num%10 + '0';          
  14.         num/=10;  
  15.         i++;  
  16.     }while(num>0);  
  17.       
  18.     if(sign<0)  
  19.     {  
  20.         temp[i++] = '-';//对于负数,要加以负号  
  21.     }  
  22.       
  23.     temp[i] = '\0';  
  24.       
  25.     i--;  
  26.       
  27.     while(i>=0)//反向操作  
  28.     {  
  29.         str[j] = temp[i];  
  30.         j++;  
  31.         i--;  
  32.     }  
  33.       
  34.     str[j] = '\0';  
  35. }  
  36.   
  37.   
  38. int atoi(char s[])  
  39. {  
  40.     int i = 0,sum = 0,sign;    //输入的数前面可能还有空格或制表符应加判断  
  41.       
  42.     while(' '==s[i]||'\t'==s[i])  
  43.     {  
  44.         i++;  
  45.     }  
  46.       
  47.     sign = ('-'==s[i])?-1:1;  
  48.       
  49.     if('-'==s[i]||'+'==s[i])  
  50.     {  
  51.         i++;  
  52.     }  
  53.       
  54.     while(s[i]!='\0')  
  55.     {  
  56.         sum = s[i]-'0'+sum*10;  
  57.         i++;  
  58.     }      
  59.       
  60.     return sign*sum;  
  61. }   


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