converts a string of hexadecimal digits into its equivalent integer value

#import 
#define key 16

void tran (char s[]) {
 int i = 0;
 int sum = 0;
 while (i  if (s[i]>='0'&&s[i]<='9') {
   sum += (s[i]-'0')*pow(key,strlen(s)-1-i);
  }else if (s[i]>='A'&&s[i]<='F'){
   sum += (s[i]-'A'+10)*pow(key, strlen(s)-1-i);
  }else if (s[i]>='a'&&s[i]<='f') {
   sum += (s[i]-'a'+10)*pow(key, strlen(s)-1-i);
  }
  i++;
 }
 printf("%s等于%d\n",s,sum);
}

//去掉回车
/***********************> ReplaceReturnAtEndOfString <*/
void    ReplaceReturnAtEndOfString( char *theString ) {
    int    length = strlen( theString );
    
    theString[ length - 1 ] = '\0';
}

int main (int argc, const char * argv[]) {
    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
 char s[20];
 loop: printf("16进制转10进制"); 
 fgets(s, 20, stdin );
 ReplaceReturnAtEndOfString(s);
 tran(s);
 goto loop;
    [pool drain];
    return 0;
}