#include 
    
     #include 
     
      int htoi(char s[]);main(){     char s1[] = "10";     char s2[] = "2D";     char s3[] = "3f";     char s4[] = "0X4F";     char s5[] = "0x3a";     printf("%s -> %d\n", s1, htoi(s1));     printf("%s -> %d\n", s2, htoi(s2));     printf("%s -> %d\n", s3, htoi(s3));     printf("%s -> %d\n", s4, htoi(s4));     printf("%s -> %d\n", s5, htoi(s5));}int htoi(char s[]){     int n = 0;     int i = -1;     while (s[++i] != '\0')    {          if (i == 0 && s[i] == '0')               continue;          else if (s[i] == 'x' || s[i] == 'X')               continue;          else if ('0'<= s[i] && s[i] <= '9')               n = n * 16 + (s[i] - '0');          else if ('a'<= s[i] && s[i] <= 'f')               n = n * 16 + (s[i] - 'a' + 10);          else if ('A' <= s[i] && s[i] <= 'F')               n = n * 16 + (s[i] - 'A' + 10);          else               return -1;     }     return n;}程序转自：http://blog.csdn.net/dc_726/article/details/7032656