浙大版《C语言程序设计（第3版）》题目集 习题7-8 字符串转换成十进制整数 (15分)

#include <stdio.h>
#define MAXN 80
int main()
{
    char str[MAXN];
    int i, number, flag;
    i = 0;
    while ((str[i] = getchar()) != '#')
        i++;
    str[i] = '\0';
    flag = 1;
    for (i = 0; str[i] != '\0'; i++)
    {
        if ((str[i] >= 'a' && str[i] <= 'f') || (str[i] >= 'A' && str[i] <= 'F') || (str[i] >= '0' && str[i] <= '9'))
            break;
        if (str[i] == '-')
        {
            flag = 0;
            break;
        }
    }
    number = 0;
    for (i = 0; str[i] != '\0'; i++)
    {
        if (str[i] >= '0' && str[i] <= '9')
            number = number * 16 + str[i] - '0';
        else if (str[i] >= 'a' && str[i] <= 'f')
            number = number * 16 + str[i] - 'a' + 10;
        else if (str[i] >= 'A' && str[i] <= 'F')
            number = number * 16 + str[i] - 'A' + 10;
    }
    if (flag)
        printf("%d", number);
    else
        printf("%d", -number);
    return 0;
}