C程序设计语言练习2-3

/*练习2-3 编写函数htoi(s),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。

字符串允许包含的数字包括：0~9、a~f、A~F。*/

#include <stdio.h>int htoi(char s[]);int main(){int a = htoi("1234");int b = htoi("0x1f");int c = htoi("0XAD");printf("十进制:%d, 十六进制:%#x\n",a,a);printf("十进制:%d, 十六进制:%#x\n",b,b);printf("十进制:%d, 十六进制:%#x\n",c,c);return 0;}int htoi(char s[]){int n,i ;n = 0;for (i=0;s[i]!='\0';i++){if (s[i]=='0'&&(s[i+1]=='x'||s[i+1]=='X')){i = i+2;}if((s[i]>='0'&&s[i]<='9')){n = n*16+s[i]-'0';}else if (s[i]>='a'&&s[i]<='f'){n = n*16+10+s[i]-'a';}else if (s[i]>='A'&&s[i]<='F'){n = n*16+10+s[i]-'A';}}return n;}