问题描述
**问题在于它不起作用，因为它会一直为所有平均值打印A。即使一个人的平均分是30，它仍然说您的平均分是30，而您的成绩是A。**
#include<iostream>
#include<string>
using namespace std;
#define newline '\n';
int main()
{
int studentno;
string name;
float marks[8];
float sum=0;
double average;
cout<<"Please enter your full names"<<newline;
getline(cin,name);
cout<<endl;
cout<<"Please enter your student number :"<<newline;
cin>>studentno;
cout<<endl;
for(int i = 0; i<8; i++)
{
cout<<"Please enter the marks of the student :";
cin>>marks[i];
cout<<endl;
sum += marks[i];
}
average = sum/8;
#So from this point,I have subdivided the sections into different ranges whereby if a person has an average of 85 then its an A,and if an average of 76 then its an A-. The problem is it doesn't work since it keeps printing an A for all averages.
if(80.0<= average <=100)
{
cout<<"Your average is :"<<average<<" and your grade is A "<<endl;
}
else if(75.0<= average <=79.9)
{
cout<<"Your average is :"<<average<<" and your grade is A- "<<endl;
}
else if(70.0<= average <=74.9)
{
cout<<"Your average is :"<<average<<" and your grade is B+ "<<endl;
}
else if(65.0<= average <=69.9)
{
cout<<"Your average is :"<<average<<" and your grade is B "<<endl;
}
else if(60.0<= average <=64.9)
{
cout<<"Your average is :"<<average<<" and your grade is B- "<<endl;
}
else if(55.0<= average <=59.9)
{
cout<<"Your average is :"<<average<<" and your grade is C+ "<<endl;
}
else if(50.0<= average <=54.9)
{
cout<<"Your average is :"<<average<<" and your grade is C "<<endl;
}
else if(45.0<= average <=49.9)
{
cout<<"Your average is :"<<average<<" and your grade is C- "<<endl;
}
else if(40.0<= average <=44.9)
{
cout<<"Your average is :"<<average<<" and your grade is D+ "<<endl;
}
else if(35.0<= average <=39.9)
{
cout<<"Your average is :"<<average<<" and your grade is D "<<endl;
}
else if(31.0<= average <=34.9)
{
cout<<"Your average is :"<<average<<" and your grade is D- "<<endl;
}
else if(0.0<= average <=30.9)
{
cout<<"Your average is :"<<average<<" and your grade is E "<<endl;
}
else
{
cout<<"Invalid marks input please check again and correct where you went wrong"<<endl;
}
return 0;
}
这是输出
Please enter your full names
James Bond
Please enter your student number :
007
Please enter the marks of the student :12
Please enter the marks of the student :20
Please enter the marks of the student :30
Please enter the marks of the student :23
Please enter the marks of the student :24
Please enter the marks of the student :21
Please enter the marks of the student :7
Please enter the marks of the student :13
Your average is :18.75 and your grade is A
如您所见，它说平均分数18.75等于A，这不是我在代码上写的。
解决方法
这种情况
if(80.0<= average <=100)
不检查average是否在80到100之间。
相反，条件的计算结果为if((80.0<= average) <=100)，结果为if(0 <=100)或if(1 <=100)，两者始终为真，因此您总是得到平均成绩为{ {1}}。
进行检查的正确方法是：
A