C++ if-else - 吾爱学编程

在 C++ 编程中，if 语句用于测试条件。C++ 中有多种类型的 if 语句。

if 语句
if-else 语句
嵌套 if 语句
if-else-if

C++ if 语句

C++ if 语句测试条件。如果条件为真则执行。

if(condition)
{ 
//code to be executed 
}

C++ if 示例

#include <iostream> 
using namespace std; 

int main () 
{ 
   int num = 10; 
   if (num % 2 == 0) 
   { 
      cout<<"It is even number"; 
   } 
   return 0; 
}

输出

It is even number

C++ if-else 语句

C++ if-else 语句也测试条件。如果条件为真，则执行 if 块，否则执行 else 块。

if(condition)
{ 
//code if condition is true 
}
else
{ 
//code if condition is false 
}

C++ if-else 示例

#include <iostream> 
using namespace std; 
int main () 
{ 
int num = 11; 
if (num % 2 == 0) 
{ 
cout<<"It is even number"; 
} 
else 
{ 
cout<<"It is odd number"; 
} 
return 0; 
}

输出：

It is odd number

C++ if-else 示例：使用来自用户的输入

It is odd number#include <iostream> 
using namespace std; 
int main () 
{ 
int num; 
cout<<"Enter a Number: "; 
cin>>num; 
if (num % 2 == 0) 
{ 
cout<<"It is even number"<<endl; 
} 
else 
{ 
cout<<"It is odd number"<<endl; 
} 
return 0; 
}

输出：

Enter a number:11
It is odd number

输出：

Enter a number:12
It is even number

C++ if-else-if 阶梯语句

C++ if-else-if 语句从多个语句执行一个条件。

if(condition1)
{ 
//code to be executed if condition1 is true 
}else if(condition2)
{ 
//code to be executed if condition2 is true 
} 
else if(condition3)
{ 
//code to be executed if condition3 is true 
} 
... 
else
{ 
//code to be executed if all the conditions are false 
}

C++ if else-if 示例

#include <iostream> 
using namespace std; 
int main () 
{ 
int num; 
cout<<"Enter a number to check grade:"; 
cin>>num; 
if (num <0 || num >100) 
{ 
cout<<"wrong number"; 
} 
else if(num >= 0 && num < 50){ 
cout<<"Fail"; 
} 
else if (num >= 50 && num < 60) 
{ 
cout<<"D Grade"; 
} 
else if (num >= 60 && num < 70) 
{ 
cout<<"C Grade"; 
} 
else if (num >= 70 && num < 80) 
{ 
cout<<"B Grade"; 
} 
else if (num >= 80 && num < 90) 
{ 
cout<<"A Grade"; 
} 
else if (num >= 90 && num <= 100) 
{ 
cout<<"A+ Grade"; 
} 
}

输出：

Enter a number to check grade:66
C Grade

输出：

Enter a number to check grade:-2
wrong number