the c programming language 2-3

#include<stdio.h>

#define MAXLINELEN 1000

int power(int base,int n)

{

 int i=;

 int answer=;

 for(i=;i<n;i++)

 answer=answer*base;

 return answer;

}

/*strlen函数:返回s的长度*/

int strlen(char *s)

{

 int i;

 i=;

 while(s[i]!='\0')

 ++i;

 return i;

}

/*getline函数*/

void getlines(char *s)

{

 int i=;

 int lim=MAXLINELEN;

 int c;

 for(i=;i<lim-&&(c=getchar())!='\n'&&c!=EOF;i++)

 s[i]=c;

}

/*hexalpha_to_int函数：把单个char转换成int*/

int hexalpha_to_int(int c)

{

  if(c>=''&&c<='')

  c=c-'';

  else if(c>='a'&&c<='z')

  c=c-'a'+;

  else if(c>='A'&&c<='Z')

  c=c-'A'+;

  return c;

}

/**/

int htoi(char s[])

{

 int len;

 int i;

 len=strlen(s);

 int answer=;

 if(s[]==''&&(s[]=='X'||s[]=='x'))

 {

  for(i=;i<len;i++)

  {

   answer=hexalpha_to_int(s[i])*power(,len--i)+answer;

  }

 }

 else

 {

  for(i=;i<len;i++)

  {

   answer=hexalpha_to_int(s[i])*power(,len--i)+answer;

   printf("i:%d\n",i);

   printf("hexalpha_to_int(s[i]):%d\n",hexalpha_to_int(s[i]));

   printf("power(16,len-1-i):%d\n",power(,len--i));

   printf("answer:%d\n",answer);

  }

 }

 return answer;

}

main()

{

 char s[MAXLINELEN];

 getlines(s);

 printf("%d\n",htoi(s));

}