虽然我有一个语句，如果用户输入q或输入无效语句将退出程序，if和if else语句后面的代码仍会显示。例如，如果用户输入q，代码将编译并读取：＆＃34;您已选择退出程序。感谢您使用该程序！＆＃34;但是它也会将重量和旅行时间显示为0。
int main()
{
string planet;
char selection;
double weightEarth = 0;
double rate = 0;
double distanceFromSun = 0;
double surfaceGravity = 0;
double newWeight = 0;
double travelTime = 0;
double travelDistance = 0;
double distanceFromPlanets = 0;
double distanceFromEarthToSun = 93.0;
cout << "INTERPLANETARY TRAVEL MENU\n"
<< "----------------------------\n"
<< "a) Mercury\n"
<< "b) Venus\n"
<< "c) Earth\n"
<< "d) Mars\n"
<< "e) Jupiter\n"
<< "f) Saturn\n"
<< "g) Uranus\n"
<< "h) Neptune\n"
<< "q) Quit\n"
<< "Select a planet to travel to or q to quit the program :\n";
cin >> selection;
if (selection <= 'h')
{
cout << "Please enter your weight: \n";
cin >> weightEarth;
cout << "At what speed would you like to travel at?\n";
cin >> rate;
if (selection == 'a')
{
planet = "Mercury";
surfaceGravity = 0.27;
distanceFromSun = 36;
}
else if (selection == 'b')
{
planet = "Venus";
surfaceGravity = 0.86;
distanceFromSun = 67.0;
}
else if (selection == 'c')
{
planet = "Earth";
surfaceGravity = 1.00;
distanceFromSun = 93.0;
}
else if (selection == 'd')
{
planet = "Mars";
surfaceGravity = 0.37;
distanceFromSun = 141.0;
}
else if (selection == 'e')
{
planet = "Jupiter";
surfaceGravity = 2.64;
distanceFromSun = 483.0;
}
else if (selection == 'f')
{
planet = "Saturn";
surfaceGravity = 1.17;
distanceFromSun = 886.0;
}
else if (selection == 'g')
{
planet = "Uranus";
surfaceGravity = 0.92;
distanceFromSun = 1782.0;
}
else
{
planet = "Neptune";
surfaceGravity = 1.44;
distanceFromSun = 2793.0;
}
}
else if (selection == 'q')
{
cout << "You have chosen to quit the program. Thank you for using the program!\n";
}
else
{
cout << "You have entered an invalid selection.\n";
}
newWeight = weightEarth * surfaceGravity;
distanceFromPlanets = abs(distanceFromSun - distanceFromEarthToSun);
travelTime = travelDistance / rate;
cout << "Your weight on " << planet << " : " << newWeight << endl;
cout << "Your travel time to " << planet << ":\n";
答案 0 :(得分：1)
您的q和invalid选择路径仅打印到控制台，它们不会退出程序。您需要每个return 0;。
但更好的方法是使用设置的布尔值，如果要退出或选择无效。
这是一种方法。
将布尔值声明为真
bool validPlanet = true;
在quit和invalid路径中添加此声明
validPlanet = false;
然后将您的体重计算包裹在if条件下，如此
if( validPlanet)
{
newWeight = weightEarth * surfaceGravity;
distanceFromPlanets = abs(distanceFromSun - distanceFromEarthToSun);
travelTime = travelDistance / rate;
cout << "Your weight on " << planet << " : " << newWeight << endl;
cout << "Your travel time to " << planet << ":\n";
}
我假设您之后立即有return 0;，否则您需要使用validPlanet来确保这些语句被恰当地调用。
答案 1 :(得分：0)
一种简单的方法是将getch()放在语句后跟exit(0);
如果部分成为最后的其他部分：
else if (selection == 'q')
{
cout << "You have chosen to quit the program. Thank you for using the program!\n";
getch(); //stops the current screen until a key stroke
exit(0); //exits the program. (zero value in the argument tells that it was a safe exit)
}
或者，如果您不希望用户在退出前给出击键，您可以使用delay(time)功能停止屏幕特定时间。
然后代码变为：
else if (selection == 'q')
{
cout << "You have chosen to quit the program. Thank you for using the program!\n";
delay(1000) //stops the current screen for 1 second. (time in miliseconds, 1000ms = 1 second)
exit(0); //exits the program. (zero value in the argument tells that it was a safe exit)
}
答案 2 :(得分：0)
您的代码根据您的需要重新格式化 （因为我们还没有在if语句中使用布尔值。目前我还在尝试重新使用构造我的if和if else语句来解决问题，但我似乎无法得到正确的组合。）
double weightEarth = 0; //made these variables global so that display_result()can access it.
double rate = 0;
double distanceFromSun = 0;
double surfaceGravity = 0;
double newWeight = 0;
double travelTime = 0;
double travelDistance = 0;
double distanceFromPlanets = 0;
double distanceFromEarthToSun = 93.0;
void display_result()
{
newWeight = weightEarth * surfaceGravity;
distanceFromPlanets = abs(distanceFromSun - distanceFromEarthToSun);
travelTime = travelDistance / rate;
cout << "Your weight on " << planet << " : " << newWeight << endl;
cout << "Your travel time to " << planet << ":\n";
}
int main()
{
string planet;
char selection;
cout << "INTERPLANETARY TRAVEL MENU\n"
<< "----------------------------\n"
<< "a) Mercury\n"
<< "b) Venus\n"
<< "c) Earth\n"
<< "d) Mars\n"
<< "e) Jupiter\n"
<< "f) Saturn\n"
<< "g) Uranus\n"
<< "h) Neptune\n"
<< "q) Quit\n"
<< "Select a planet to travel to or q to quit the program :\n";
cin >> selection;
if (selection <= 'h')
{
cout << "Please enter your weight: \n";
cin >> weightEarth;
cout << "At what speed would you like to travel at?\n";
cin >> rate;
if (selection == 'a')
{
planet = "Mercury";
surfaceGravity = 0.27;
distanceFromSun = 36;
display_result();
}
else if (selection == 'b')
{
planet = "Venus";
surfaceGravity = 0.86;
distanceFromSun = 67.0;
display_result();
}
else if (selection == 'c')
{
planet = "Earth";
surfaceGravity = 1.00;
distanceFromSun = 93.0;
display_result();
}
else if (selection == 'd')
{
planet = "Mars";
surfaceGravity = 0.37;
distanceFromSun = 141.0;
display_result();
}
else if (selection == 'e')
{
planet = "Jupiter";
surfaceGravity = 2.64;
distanceFromSun = 483.0;
display_result();
}
else if (selection == 'f')
{
planet = "Saturn";
surfaceGravity = 1.17;
distanceFromSun = 886.0;
display_result();
}
else if (selection == 'g')
{
planet = "Uranus";
surfaceGravity = 0.92;
distanceFromSun = 1782.0;
display_result();
}
else
{
planet = "Neptune";
surfaceGravity = 1.44;
distanceFromSun = 2793.0;
display_result();
}
}
else if (selection == 'q')
{
cout << "You have chosen to quit the program. Thank you for using the program!\n";
}
else
{
cout << "You have entered an invalid selection.\n";
}
}
我创建了一个函数display_result()并移动了在退出if-else语句时运行的代码。现在只有在您尝试计算重量时才会调用此项，而不是在您退出程序时调用。这解决了程序复杂性和程序冗长的问题。