/** 將十六進制數字組成的字符串（包含可選的前綴0x或0X）轉換為與之等價的整型值*/#include <stdio.h>#include <math.h>/* 將十六進制中的字符裝換為對應的整數 */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; /* 非十六進制字符 */ } 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; /* 有效性檢查 */ 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);}