C++如果语句导致CMD不发布输出？

Question

我在C++中做了BMI计算，并决定我想添加一个计算每周体重变化的用户新BMI的部分（比如每周减掉2磅，或者每周增加2磅，n周）我有两个if语句，所以当被问及他们在寻找什么样的重量变化时，基于这个结果，它会跳到一个if语句或另一个语句。我的意思是，如果用户想要重量，他们会把-2，这将跳转到我为减肥设置的if语句。如果用户想要GAIN权重，它会跳转到另一个if语句，设置为计算新的BMI并给定新的权重变化。这里是我的两个if语句设置：

#include "stdafx.h" 
#include <iostream> // Allows us to use cout and cin 
#include <cmath> // To allow us to calculate the BMI 
#include <iomanip> // Set specific decimal points(two) 
using namespace std; 

int main() 
{ 
double weight; 
cout << "What is your current weight?: "; // Using the cout() function, we get user input 
cin >> weight; 
double heightFeet; 
cout << "What is your height(in feet, just the first part(Example, if you're 5'11, put 5)"; 
cin >> heightFeet; 
double heightInches; 
cout << "What is your height in inches, just the second part(Example if you're 5'11, put 11)\n"; 
cin >> heightInches; 
double HeightConverter = 12 * heightFeet + heightInches; 
cout << "Your height in inches is: " << HeightConverter << "\n"; 
double BMICalc = (weight * 703)/(pow(HeightConverter, 2)); 
std::cout << std::fixed; 
std::cout << std::setprecision(2); 
std::cout << "Your current BMI is: " << BMICalc << "\n"; 
double GoalWeight; 
std::cout << "What is your goal weight change per week? (lb)\n"; 
cin >> GoalWeight; 
if (GoalWeight >= 0) { 
    int weeks; 
    cout << "How many weeks do you plan to continue this trend?\n"; 
    cin >> weeks; 
    double PosBMI = (weight + GoalWeight) * 703/(pow(HeightConverter, 2)); 
    cin >> PosBMI; 
    cout << "If you complete your plan for " << weeks << "weeks you will have a new BMI of: \n" << PosBMI; 

} 
if (GoalWeight < 0) { 
    int weeks; 
    cout << "How many weeks do you plan to continue this trend?\n"; 
    cin >> weeks; 
    double NegBMI = (weight - GoalWeight) * 703/(pow(HeightConverter, 2)); 
    cin >> NegBMI; 
    cout << "If you complete your plan for " << weeks << "weeks you will have a new BMI of: \n" << NegBMI; 
} 
system("pause"); 
return 0; 

} 

当这个被编译，它得到“多少周做你打算继续这一趋势？”，如果我输入3，它会在终端暂停3，并且什么都不做，最终我必须关闭它。有没有人看到这个问题在if语句中是什么？对于丑陋的代码，以及提前抱歉。在这里忍受我。

Answer 1

PosBMI被声明和初始化，然后立即被std :: cin调用覆盖的大问题。类似的NegBMI问题。

double PosBMI = (weight + GoalWeight) * 703/(pow(HeightConverter, 2)); 
cin >> PosBMI; 

然后，当然，重量没有宣布......我认为你需要先得到这个编译。

所有这一切，我想补充一点，我的个人BMI需要工作。

我想，你的代码更可能应该是（伪codish这里）

cout << "Enter your weight"; 
cin >> weight; 
cout << "Enter Goal" 
cin >> WeightGoal 

if (WeightGoal > weight) { 
    ..... 
} else { 
    .... 
} 
cout << "If you complete your plan for " << weeks << .....