您好我希望有人能帮我解决我做错的事。这是我要指出的功课，但需要有人告诉我我是一个多么蠢，因为我没有看到我做错了什么。
我应该让用户输入一个月，一天和一年来确定它是否是一个神奇的日期。那部分我已经为另一个项目做过了。我应该使用名为isDateValid的函数返回并验证日期。我很确定我错过了一些明显的东西，并且可以使用任何人的帮助。谢谢！
问题是，当我运行它时，我总是认为这是一个无效的日期！
#include <iostream>
using namespace std;
bool leapYear(int);
bool isDateValid(int, int, int);
int main()
{
int month, day, year;
cout << "Is the date you are thinking of a magic one? Let's see...\n";
cout << "What is the month in numeric form only? "; cin >> month;
cout << "What is the day of the month? "; cin >> day;
cout << "What is the four digit year? "; cin >> year;
if (isDateValid(month, day, year) == false)
{
cout << "The date you entered, "<< month << "/" << day << "/" <<
year << " is NOT a VALID Date.\n";
cout << "If you think I am wrong, please feel free to run me again";
}
else if (month * day == year % 100) // if true then do this
{
cout << "The date you entered, " <<
month << "/" << day << "/" << year << " is a magic date!!\n";
}
else // if false then do this
{
cout << "The date you entered, " << month << "/" << day << "/" <<
year << " is NOT a magic date!!\n";
}
//Program ID
cout <<"\n" << "L5P1LB.cpp\n" << "11-26-12\n" << endl;
system ("pause");
return 0;
}//end main
// isDateValid function to validate date entered
bool isDateValid(int month, int day, int year)
{
bool validation = true;
if(!(year >= 1600 && year <=2100))
validation = false;
if(leapYear(year))
{
if ((month == 2) && (day > 29))
validation = false;
}
else if(!leapYear(year))
{
if ((month == 2) && (day > 28))
validation = false;
}
if((month < 1 && month > 12) || (day < 1))
validation = false;
if((month == 1) || (month ==3) || (month == 5) || (month == 7) ||
(month == 8) || (month == 10) || (month == 12) && (day > 31))
validation = false;
else if (((month == 4) || (month == 6) || (month == 9) || (month == 11)) &&
(day > 30))
validation = false;
else
validation == true;
return validation;
}
// leapYear function to determine if the year is a leap year for validation
bool leapYear(int year)
{
return(year % 100 != 0 && year % 4 == 0) || (year % 400 == 0);
} // end leapYear
修改
好的，现在我的问题是我没有得到它不是一个有效的日期。它一起跳过验证，只是运行它的“魔术日期”部分！
这里是重写加上我的完整代码，希望在Dropshed中正确缩进。
Description: This program determines if when the user enters a month,
day, and four digit year which will then be stripped down to its
two digit year and determined to be a magic date if the day entered
multiplied by the month entered equals the years two digit format.
Design:
begin main
input data
Ask user for a month in number form
Ask user for a day of the month
Ask user for four digit month
Validate
begin isDateValid
if year is between 1600 and 2100, inclusive then return
true
if month is between 1 and 12, inclusive return true
if month is Jan, Mar, May, July, Aug, Oct, Dec
then if day is between 1 and 31 inclusive return true
if month is Apr, June, Sept, Nov
then if day is between 1 and 30 inclusive return true
if month is Feb
then determine if leap year by running function
leapYear provided for us.
if leap year is true
then if day is between 1 and 29, inclusive return true
if not leap year then if day is between 1 and 28,
inclusive then return true
end isDateValid
if isDateValid is true then
Calculate
if the month times the year is equal to the year modulus 100
then output it is a magic date
if it does not equal the year in 2 digit form
then output that it is not a magic date
else output error message
Output Program ID
end main
The output needs to include the books data of 6/10/1960 */
#include <iostream>
using namespace std;
bool leapYear(int);
bool isDateValid(int, int, int);
int main()
{
int month, day, year;
cout << "Is the date you are thinking of a magic one? Let's see...\n";
cout << "What is the month in numeric form only? "; cin >> month;
cout << "What is the day of the month? "; cin >> day;
cout << "What is the four digit year? "; cin >> year;
if (isDateValid(month, day, year) == false)
{
cout << "The date you entered, "<< month << "/" << day << "/" <<
year << " is NOT a VALID Date.\n";
cout << "If you think I am wrong, please feel free to run me again";
}
else if (month * day == year % 100) // if true then do this
{
cout << "The date you entered, " <<
month << "/" << day << "/" << year << " is a magic date!!\n";
}
else // if false then do this
{
cout << "The date you entered, " << month << "/" << day << "/" <<
year << " is NOT a magic date!!\n";
}
//Program ID
cout <<"\n" << "L5P1LB.cpp\n" << "11-26-12\n" << endl;
system ("pause");
return 0;
} //end main
// isDateValid function to validate date entered
bool isDateValid(int month, int day, int year)
{
bool validation = true; // validation set to true
// if it is not between 1600 and 2100 then set to false
if(!(year >= 1600 && year <=2100))
validation = false;
// call leapYear function
if(leapYear(year))
{
// if February and day is greater than 29 then set to false
if ((month == 2) && (day > 29))
validation = false;
}
// else if NOT leapYear
else if(!leapYear(year))
{
// if February and day is greater then 28 then set to false
if ((month == 2) && (day > 28))
validation = false;
}
// if month is less then 1 and over 12 then set to false
if((month < 1 && month > 12))
validation = false;
// if day is less then 1 then set to false
if(day < 1)
validation = false;
// if month is 1 (Jan), 3 (Mar), 5 (May), 7 (July), 8 (Aug), 10 (Oct),
// or 12 (Dec) and day is greater then 31 set to false
if((month == 1) || (month ==3) || (month == 5) || (month == 7) ||
(month == 8) || (month == 10) || (month == 12) && (day > 31))
validation = false;
// if month is 4 (Apr), 6 (June), 9 (Sept), or 11 (Nov) and day is
// greater then 30 set to false
if (((month == 4) || (month == 6) || (month == 9) || (month == 11)) &&
(day > 30))
validation = false;
// else everything that is left set validation to true
else
validation = true;
return validation;
} // End isDateValid
// leapYear function to determine if the year is a leap year for validation
bool leapYear(int year)
{
return(year % 100 != 0 && year % 4 == 0) || (year % 400 == 0);
} // end leapYear
对不起，如果我放错了地方或任何东西！
也感谢您的帮助。真的很感激。
答案 0 :(得分：3)
您在日期验证中遇到了一些错误。
Luchian指出的运算符优先级是1，但是你还有其他几个：
month < 1 && month > 12 - 这是不可能的，一个月不能小于1且大于12 validation == true没有做任何事情。 ==是一个比较运算符。幸运的是，这不会影响您的功能，因为validation在到达此代码时已经true。我冒昧地用我认为更清洁的方式重写它，但如果您愿意保留您的版本，您可以修改month检查
bool isDateValid(int month, int day, int year)
{
bool validation = true;
if(!(year >= 1600 && year <=2100))
validation = false;
if(day < 1)
validation = false;
switch(month)
{
case 2:
if(leapYear(year)) // We only care about leap years in February
if(day > 29)
validation = false;
else
if(day > 28)
validation = false;
break;
case 1: case 3: case 5: case 7: case 8: case 10: case 12:
if(day > 31)
validation = false;
break;
case 4: case 6: case 9: case 11:
if(day > 30)
validation = false;
break;
default: // the month is not between 1 and 12
validation = false;
break;
}
return validation;
}
答案 1 :(得分：1)
||正在短路，因此(month == 1) || (month ==3) || (month == 5) || (month == 7) ||
(month == 8) || (month == 10) || (month == 12) && (day > 31)如果满足第一个条件则评估为true。您需要添加一组额外的括号：
((month == 1) || (month ==3) || (month == 5) || (month == 7) ||
(month == 8) || (month == 10) || (month == 12)) && (day > 31)
其他月份相同。
此外，
validation == true;
是无操作，您可能需要validation = true。
答案 2 :(得分：0)
就个人而言，我建议更直接，更简洁。 ?三元运算符起初可能有点混乱，但一旦清楚地理解就很简单。我认为它是一种可以嵌入表达式中的“if-else”。
bool isDateValid(int month, int day, int year)
{
return year >= 1600 && year<= 2100 &&
month >= 1 && month <= 12 &&
day >= 1 &&
day <= (month == 2 ? (leapyear(year) ? 29 : 28) :
month == 9 || month == 4 || month == 6 || month == 11 ? 30 : 31);
// "30 days has September, April, June and November..."
}
如果对月常量使用枚举，则可能会更具可读性：
enum Month { Jan = 1, Feb, Mar, Apr ... };
目标是实际编码：
day <= (month == Feb ? ...