为什么我的 while 语句没有结束？

Why doesn't my while statement end?

本文关键字：结束 语句 我的 while 为什么      更新时间：2023-10-16

我创建了这个程序来计算人们测试的分数并计算成绩的数量。我想发生的是，当用户在程序询问"输入学生姓名"时输入"//"时，while 语句应该结束，或者这就是我认为应该发生的事情。实际发生的是我键入"//"，然后程序要求分数，然后 while 语句结束。为什么会这样，我应该怎么做才能解决它？

#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
string name, grade;
int score;
int count1 = 0;
int acount = 0;
int bcount = 0;
int ccount = 0;
int dcount = 0;
int fcount = 0;
while (name != "//") {
cout << "Enter Student Name n";
cin >> name;
cout << "Enter Student Score n";
cin >> score;
count1 += 1;
if (score >= 90) {
grade = "A";
acount += 1;
cout << name << " " << score << " " << grade << endl;
}
else if (score >= 80) {
grade = "B";
bcount += 1;
cout << name << " " << score << " " << grade << endl;
}
else if (score >= 70) {
grade = "C";
ccount += 1;
cout << name << " " << score << " " << grade << endl;
}
else if (score >= 60) {
grade = "D";
dcount += 1;
cout << name << " " << score << " " << grade << endl;
}
else if (score <= 59) {
grade = "F";
fcount += 1;
cout << name << " " << score << " " << grade << endl;
}
};
cout << "Summary Report n" << "Total Students Count: " << count1 << endl;
cout << "A student count: " << acount << endl;
cout << "B student count: " << bcount << endl;
cout << "C student count: " << ccount << endl;
cout << "D student count: " << dcount << endl;
cout << "F student count: " << fcount << endl;
return 0;
}

大部分事情已经在评论中说过了：

您的问题是，您希望循环持续检查其状况，但事实并非如此。

while(name != "//") // here the condition is evaluated
{
name = "//";    // here it is not 
// the following code is executed, independent of the current name value
} // here the program jumps back to the loop condition, which is now false and it will not enter another time.

如评论中所述，可行的替代方案可能是：

while(true)
{
std::cin >> name;
if(name == "//")
break;
else
evaluateScore();
}

试试这个：

#include "stdafx.h"
#include <iostream>
#include <string>
using namespace std;
int main()
{
string name, grade;
int score;
int count1 = 0;
int acount = 0;
int bcount = 0;
int ccount = 0;
int dcount = 0;
int fcount = 0;
while (true) {  // keep running the loop
cout << "Enter Student Name n";
cin >> name;
if(name == "//")  // if "//" found, break the loop
break;
cout << "Enter Student Score n";
cin >> score;
count1 += 1;
if (score >= 90) {
grade = "A";
acount += 1;
cout << name << " " << score << " " << grade << endl;
}
else if (score >= 80) {
grade = "B";
bcount += 1;
cout << name << " " << score << " " << grade << endl;
}
else if (score >= 70) {
grade = "C";
ccount += 1;
cout << name << " " << score << " " << grade << endl;
}
else if (score >= 60) {
grade = "D";
dcount += 1;
cout << name << " " << score << " " << grade << endl;
}
else if (score <= 59) {
grade = "F";
fcount += 1;
cout << name << " " << score << " " << grade << endl;
}
};
cout << "Summary Report n" << "Total Students Count: " << count1 << endl;
cout << "A student count: " << acount << endl;
cout << "B student count: " << bcount << endl;
cout << "C student count: " << ccount << endl;
cout << "D student count: " << dcount << endl;
cout << "F student count: " << fcount << endl;
return 0;
}
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