/*
* 将十六进制数字组成的字符串（包含可选的前缀0x或0X）转换为与之等价的整型值
*/
#include <stdio.h>
#include <math.h>
/* 将十六进制中的字符装换为对应的整数 */
int hexchtoi(char hexch )
{
 char phexch[] = \"ABCDEF\";
 char qhexch[] = \"abcdef\";
 int i;
 for(i=0;i<6;i++){
  if((hexch == phexch[i]) || (hexch == qhexch[i]))
   break;
 }
 printf(\"i=%d\",i);
 if(i >= 6){
  return 0; /* 非十六进制字符 */
 }
 return 10+i;
}
int htoi(char s[])
{
 int n=0; /*有n位*/
 int valu=1; /*是否有效*/
 int i=0,j;
 int answer=0;
 /* 有效性检查 */
 if((s[0] == \'0\') && ((s[1] == \'x\') || (s[1] == \'X\'))){
  i += 2;
 }
 while((s[i] != \'\\n\')){
  if((s[i] < \'0\') && (s[i] > \'9\')){
   if(hexchtoi(s[i]) == 0){
    valu=0;
    break;
   }
  }
  n++;
  i++;
 }
 if(valu != 0){   
  for(j=0;j<n;j++){
   answer += ((int)pow(16,j) * hexchtoi(s[i-j-1]));
  } 
 }
 else
  answer = -1;
 return answer;
}
main()
{
 char *n[] = {\"0x7ff0\",\"0x2341\"};
 printf(\"%s is %d\\n\",n[0],htoi(n[0]));
 printf(\"%s is %d\\n\",n[0],123);
}