因此，代码将运行，但是当firstE-fourthE变量等于0时，计算total和average变量的计算。当然有一种方法可以在代码中重新定义它们或重新计算它们吗？我为可怕的格式和缩进道歉，这个网站非常挑剔。
#include <iostream>
using namespace std;
int main()
{
char fi = '\0', mi = '\0', li = '\0', end = '\0';
float firstE = 0,
secondE = 0,
thirdE = 0,
fourthE = 0,
total = firstE + secondE + thirdE + fourthE,
average = total / 4;
cout << "This program will calculate the average of a student's exam grades." << endl;
cout << "Please enter the first initial of the student's name: ";
cin >> fi;
cout << "Please enter the middle initial of the student's name: ";
cin >> mi;
cout << "Please enter the last initial of the student's name: ";
cin >> li;
cout << "Please enter the student's first exam score: ";
cin >> firstE;
cout << "Please enter the student's second exam score: ";
cin >> secondE;
cout << "Please enter the student's third exam score: ";
cin >> thirdE;
cout << "Please enter the student's fourth exam score: ";
cin >> fourthE;
/*float total = firstE + secondE + thirdE + fourthE,
average = total / 4;*/
cout << "Student's initials: " << fi << mi << li << endl;
cout << "Exam 1: " << firstE << endl;
cout << "Exam 2: " << secondE << endl;
cout << "Exam 3: " << thirdE << endl;
cout << "Exam 4: " << fourthE << endl;
cout << "Total: " << total << endl;
cout << "Average: " << average << endl;
cin >> end;
}
答案 0 :(得分：2)
你为什么要进行计算之前你甚至有值进行计算？您的代码序列应为：
1. define variables
2. get input from user
3. do calculations
4. present results
在你去商店购买鸡蛋/牛奶/糖之前，你想吃蛋糕，更不用说混合/烘烤了。
答案 1 :(得分：0)
如何在代码中定义变量或重新计算变量？
喜欢这个
#include <iostream>
int main()
{
int a; // define it once
int b; // define it once
int c; // define it once
int total; // define it once
a = 2; // change its value
b = 4;
c = 1;
total = a + b + c; // or calculate its value
std::cout << "total: " << total << '\n';
a = 9; // change its value AGAIN
b = 1;
c = 12;
total = a + b + c; // and calculate its value AGAIN
std::cout << "total: " << total << '\n';
}
答案 2 :(得分：0)
要从代码中获得所需的行为，您需要计算输入后的总数和平均值。假设成绩是整数，您可以使用int来存储每个考试成绩：
#include <iostream>
int main()
{
char fi = '\0', mi = '\0', li = '\0', end = '\0';
int firstE = 0,
secondE = 0,
thirdE = 0,
fourthE = 0,
/*IO*/
float average = (firstE + secondE + thirdE + fourthE)/4;
/*IO*/
return 0;
}
这将为您提供工作代码。
我们可以进一步清理它。为什么我们无法将John Edward Smith的首字母存储为"JES"而不是单独输入每个字符？
#include <iostream>
#include <string>
int main()
{
std::string student_initials;
int firstE = 0,
secondE = 0,
thirdE = 0,
fourthE = 0,
std::cout << "This program will calculate the average of a student's exam grades." << endl;
std::cout << "Please enter the student's initials: ";
std::cin >> student_initials;
/*MORE IO*/
float average = (firstE + secondE + thirdE + fourthE)/4;
std::cout << "Student's initials: " << student_initials << std::endl;
/*MORE IO*/
return 0;
}
更好的是，用户界面更简单一些。但是，如果学生参加额外的考试怎么办？如果他们只拿3个怎么办？您要么无法输入所有结果，要么数学错误。 我们可以为可以处理结果输入的代码引入一个循环：
#include <iostream>
#include <string>
#include <sstream>
int main()
{
/* STUFF */
int total;
int exam_result;
int exam_count = 1;
string input;
//this loop will capture multiple exam results (safely)
do
{
std::cout << "Please enter the results of exam #" << exam_count \
<< "\nleave blank if all results have been entered" << std::endl;
std::getline (std::cin, input);
stringstream(input) >> exam_result;
if (exam_result)
{
total += exam_result;
exam_count++;
}
} while (exam_result);
float average = total/exam_count;
/* STUFF */
return 0;
}
这使用一种处理cin的安全方法捕获多个检查结果（以及总数和计数）
但是它会阻止您在平均值之前打印出每个单独的结果，但是您可以将它们存储在std::vector中并迭代它们来执行此操作。我会把它留给你。
最终代码：
#include <iostream>
#include <string>
#include <sstream>
int main()
{
std::string student_initials;
std::cout << "This program will calculate the average of a student's exam grades." << endl;
std::cout << "Please enter the student's initials: ";
std::cin >> student_initials;
int total;
int exam_result;
int exam_count = 1;
string input;
//this loop will capture multiple exam results (safely)
do
{
std::cout << "Please enter the results of exam #" << exam_count \
<< "\nleave blank if all results have been entered" << std::endl;
std::getline (std::cin, input);
stringstream(input) >> exam_result;
if (exam_result)
{
total += exam_result;
exam_count++;
}
} while (exam_result);
float average = total/exam_count;
std::cout << "Student's initials: " << student_initials << std::endl;
cout << "Total: " << total << endl;
cout << "Average: " << average << endl;
return 0;
}