Question

#include<iostream>
#include<cstdio>

using namespace std;

class Time
{
    int hours=0,scan_hours=0;
    int minutes=0,scan_minutes=0;

public:

void input_time_in_format_1(void)
{
    cout<<"\n\t Enter the time in the format hh:mm A.M./P.M.:  ";
    if(scanf("%d",&hours)==1)
    {
        if(scanf(":%d A.M.",&minutes)==1)
        {   
            hours=(hours+12)%24;
                if(hours>13||minutes>60||hours<0||minutes<0)
                {   
                    cout<<"\n\t Wrong entry";
                    hours=minutes=0;
                }
                else    
                    cout<<"\n\t Your time has been accepted";
        }
        else if(scanf(":%d P.M.",&minutes)==1)
        {
            if(hours>13||minutes>60||hours<0||minutes<0)
                {   
                    cout<<"\n\t Wrong entry";
                    hours=minutes=0;
                }

            else
                cout<<"\n\t Your time has been accepted";   
        }   
        else
        {   
            cout<<"\n\t Wrong entry";
            hours=0;
            minutes=0;
        }

    }
    else
    {   
        cout<<"\n\t Wrong entry";
        hours=0;
    }


}
void input_time_in_format_2(void)
{
    cout<<"\n\t Enter the time in the format hh:mm hours:  ";
    if(scanf("%d",&hours)==1 && hours<24)
    {
        if(scanf(":%d hours",&minutes)==1 && minutes<60)
            cout<<"\n\t Your time has been accepted";

        else
        {   
            cout<<"\n\t Wrong entry";
            hours=minutes=0;
        }
    }
    else
    {   
        cout<<"\n\t Wrong entry";
        hours=0;
    }
}


void show_time_in_format_1(void)
{
    cout<<"\n\t Showing time in 24 hours format: "<<hours<<":"<<minutes<<" hours";
}

void show_time_in_format_2(void)
{
    if(hours>12)
        cout<<"\n\t Showing time in 12 hours format: "<<(hours%12)<<":"<<minutes<<" P.M.\n\n";
    else
        cout<<"\n\t Showing time in 12 hours format: "<<hours<<":"<<minutes<<" A.M.\n\n";
}
void add_time(void)
{
    cout<<"\n\t Please enter the hours and minutes respectively";
    cin>>scan_hours;
    cin>>scan_minutes;
    if(minutes+=scan_minutes>=60)
    {
        hours+=(scan_hours+1);
        hours%=24;
    }
    else
    {
        hours+=(scan_hours);
        hours%=24;
    }
}


};

int main()
{
    Time t1;
    int choice;
    do
    {
        cout<<"\n\t\t\t --Welcome--"<<"\n\n\t Please enter your choice \n\t1.Input time in 12 hours format\n\t2.Input time in 24 hours format\n\t3.Show time in 12 hours format\n\t4.Show time in 24 hours format\n\t5.Add user input time\n\t6.Exit....-->";
        cin>>choice;
        switch(choice)
        {
            case 1:cin.ignore();
                t1.input_time_in_format_1();
                break;

            case 2:
                t1.input_time_in_format_2();
                break;

            case 3:
                t1.show_time_in_format_2();
                break;

            case 4:
                t1.show_time_in_format_1();
                break;

            case 5:
                t1.add_time();
                break;

            case 6:
                cout<<"\n\t Thank You";
                exit(0);

            default:
                cout<<"\n\n\t Wrong entry";
                break;

        }

}while(1);

return 0;
}

这是我接受用户日期并以不同格式打印的程序。如果我选择 case 1 ，只要我想提供任何输入，天气是正确还是错误，它会导致我无限循环。我无法找出发生了什么。我想我已经处理了所有的例外情况。如果你愿意，可以随意转储它。

Answer 1

问题的最可能原因是这一行：

cin >> choice;

这是失败的，因为istream包含换行符，这会导致cin失败。

建议致电：

cin.ignore();

在输出提示/菜单之前，istream将为空，并且用户输入的菜单响应将被放入变量`choice;

在字符串处理的情况下遇到无限循环

1 个答案: