《c程序设计语言》读书笔记-十六位进制数转十进制

#include <stdio.h>

#include <stdio.h>

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