Question

请看一下本应该在明天发布的节目。该程序来自教科书，并使用三个功能。不幸的是，它提供了错误的输出：

Enter today's date (mm dd yyyy):  09 25 1977
Tomorrow's date is 00/10/25.

但有时它确实提供了正确的输出：

Enter today's date (mm dd yyyy):  10 07 2015
Tomorrow's date is 10/08/15.

我不明白为什么会这样。这是程序：

// Program to determine tomorrow's date

#include <stdio.h>
#include <stdbool.h>

struct date
{
    int month;
    int day;
    int year;
};

int main (void)
{
    struct date today1, tomorrow;
    struct date tomorrow_date (struct date today);

    printf("Enter today's date (mm dd yyyy):  ");
    scanf("%i%i%i", &today1.month, &today1.day, &today1.year);

    tomorrow = tomorrow_date (today1);

    printf ("Tomorrow's date is %.2i/%.2i/%.2i.\n", tomorrow.month, tomorrow.day, tomorrow.year % 100);

    return 0;
}
// Function to find the number of days in a month
int number_of_days (struct date d)
{
    int days;
    bool is_leap (struct date d);

    const int days_per_month[12] = {31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};

    if (is_leap (d) == true && d.month == 2)
        days = 29;
    else
        days = days_per_month[d.month - 1];

    return days;
}

// Function to determine if it's a leap year

bool is_leap (struct date d)
{
    bool leap_year;

    if ( (d.year % 4 == 0 && d.year % 100 != 0) || (d.year % 400 == 0))
        leap_year = true;
    else
        leap_year = false;

    return leap_year;
}

// Function to determine tomorrow's date using compound literals

struct date tomorrow_date (struct date today)
{
    struct date tomorrow;
    int number_of_days(struct date d);

    if (today.day != number_of_days(today))
        tomorrow = (struct date) {today.month, today.day + 1, today.year};

    else if (today.month == 12) // end of year
        tomorrow = (struct date) {1, 1, today.year + 1};

    else // end of month
        tomorrow = (struct date) {today.month + 1, 1, today.year};  

    return tomorrow;
}

谢谢！

Answer 1

扫描日期时使用格式说明符0xff。此说明符读取十进制整数，但接受C代码也接受的表单，即十六进制（0377）和八进制（08）。

输入09和sscanf被视为八进制，但它们不是合法的八进制数，因为八进制没有数字8或9.扫描在第一个非八进制数字处停止。（顺便说一句，你不能检查%i是否返回3.）

补救措施是将%d格式替换为08格式，该格式会按照人类读者的预期扫描<!doctype html> <html> <head> <title></title> <script type="text/javascript" src="script.js"></script> </head> <body> <ul id="list">  </ul> <button id="button">Get Data</button> </body> </html>。

Answer 2

通过将输入显示为09，您可以在八进制基础中输入输入。删除月份输入中的前导0。
http://www.cplusplus.com/reference/cstdio/scanf/

函数，结构，复合文字，不正确的输出

2 个答案: