K&RC编程语言练习2-3代码返回垃圾值。

将代码中的变量类型从int改为unsigned int，这样可以确保返回的值为正数。具体代码示例如下：

#include <stdio.h>
#include <ctype.h>

unsigned int htoi(const char s[]) {
    unsigned int hex_val = 0;
    int i = 0;
    if (s[0] == '0' && tolower(s[1]) == 'x') {
        i = 2;
    }
    while (s[i] != '\0') {
        if (isdigit(s[i])) {
            hex_val = 16 * hex_val + (s[i] - '0');
        } else if (isalpha(s[i])) {
            hex_val = 16 * hex_val + (tolower(s[i]) - 'a' + 10);
        } else {
            break;
        }
        i++;
    }
    return hex_val;
}

int main() {
    char s[] = "0xABCD";
    unsigned int result = htoi(s);
    printf("%u\n", result);  // 输出43981
    return 0;
}