如何检查输入是否为整数/字符串？ [英] How do I check if input is an integer/string?

问题描述

我的问题是我不知道如何插入规则，如果用户在字符串上输入一个数字，它会 cout 一个警告，说它无效，如果用户在等级上输入字符串/字符，则相同。怎么样？我一直在尝试，但公式不会工作。

  int x，cstotal = 100，extotal = 150; 
 
 double scorecs，exscore，labtotala，labtotalb，total; 
 
 string mystr =; 
 
 cout<< 计算：< \\\
< 1.实验室级<< \\\
< 2.讲座班<< \\\
< 3.退出<< \\\
; 
 cout<< 请输入数字：; 
 cin>> X; 
 switch（x）{
 case 1：
 
 cout< 计算实验室级。 << \\\
; 
 cout<< 输入学生姓名：; 
 cin>> mystr; 
 
 
 cout<< Good day，< mystr< 。请提供以下年级：< \\\
; 
 cout<< CS Score：; 
 cin>>评分
 
 cout<< 考试成绩：; 
 cin>> exscore; 
 
 
 labtotala = scorecs / cstotal * 0.6; 
 labtotalb = exscore / extotal * 0.4; 
 total = labtotala + labtotalb; 
 cout<< 您的实验室成绩是<总* 100 < \\\
; 
 system（pause）; 
 break; 
 case 2：
 cout<< 计算等级。 << \\\
; 
 cout<< 输入学生姓名：; 
 cin>> mystr; 
 cout<< Good day，< mystr< 。请提供以下年级：< \\\
; 
 cout<< CS Score：; 
 cin>>评分
 cout<< 考试成绩：; 
 
 cin>> exscore; 
 labtotala = scorecs / cstotal * 0.7; 
 labtotalb = exscore / extotal * 0.3; 
 total = labtotala + labtotalb; 
 cout<< 你的讲座成绩是<总* 100 < \\\
; 
 system（pause）; 
 break; 
  

解决方案

cin 设置 failbit 获取无效类型的输入。

  int x; 
 cin>> X; 
 
 if（！cin）{
 //输入不是整数
} 
  

您还可以使用 cin.fail（）来检查输入是否有效：

  if（cin.fail（））{
 //输入无效
} 
  pre> 
My problem here is I don't know how to insert a rule wherein if a user inputted a number on the string, it will cout a warning saying it's not valid, same with if a user inputted a string/char on the grades. How? I've been trying it but the formula won't work. 
int x, cstotal = 100, extotal = 150;

double scorecs, exscore, labtotala, labtotalb, total;

string mystr = "";

cout << "Compute for: " << "\n" << "1. Laboratory Grade " << "\n" << "2. Lecture Grade" << "\n" << "3. Exit" << "\n";
cout << "Please enter a number: ";
cin >> x;
switch (x) {
case 1:

    cout << "Compute for laboratory grade." << "\n";
    cout << "Enter Student Name: ";
    cin >> mystr;


    cout << "Good day, " << mystr << " . Please provide the following grades: " << "\n";
    cout << "CS Score: ";
    cin >> scorecs;

    cout << "Exam Score: ";
    cin >> exscore;


    labtotala = scorecs / cstotal * 0.6;
    labtotalb = exscore / extotal * 0.4;
    total = labtotala + labtotalb;
    cout << "Your Laboratory Grade is " << total * 100 << "\n";
    system("pause");
    break;
case 2:
    cout << "Compute for lecture grade." << "\n";
    cout << "Enter Student Name: ";
    cin >> mystr;
    cout << "Good day, " << mystr << " . Please provide the following grades: " << "\n";
    cout << "CS Score: ";
    cin >> scorecs;
    cout << "Exam Score: ";

    cin >> exscore;
    labtotala = scorecs / cstotal * 0.7;
    labtotalb = exscore / extotal * 0.3;
    total = labtotala + labtotalb;
    cout << "Your Lecture Grade is " << total * 100 << "\n";
    system("pause");
    break;

解决方案
cin sets a failbit when it gets input of an invalid type.
int x;
cin >> x;

if (!cin) {
    // input was not an integer
}
You can also use cin.fail() to check if the input was valid:
if (cin.fail()) {
    // input was not valid
}


                        
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