无论输入如何，C ++程序都会提供相同的输出

Question

I am writing a program that takes the weight and dimensions of a package from the user. If the weight is greater than or equal to 27, it should display that the package is too heavy. If the dimensions are greater than or equal to 0.1 meters cubed then it should display that the package is too big. For some reason, the code below runs fine but no matter what values I type in, it always outputs "Rejected: Too big and too heavy." Can anyone tell me why this is happening? I am in an introductory programming class, so I assume it is a small mistake that I've overlooked.

Thanks!

#include <iostream>

using namespace std;

double weight;
double length;
double width;
double height;
double dimensions;
bool weight_passed;
bool dimensions_passed;

int main()
{
    cout << "Enter the weight of the package in kilograms: ";
    cin >> weight;
    cout << "Enter the length of the package in meters: ";
    cin >> length;
    cout << "Enter the width of the package in meters: ";
    cin >> width;
    cout << "Enter the height of the package in meters: ";
    cin >> height;
    dimensions = length * width * height;
    if (weight >= 27)
        weight_passed = false;
    if (dimensions >= 0.1)
        dimensions_passed = false;

    if (dimensions_passed == false && weight_passed == false)
        cout << "Rejected: Too big and too heavy." << endl;
    else if (dimensions_passed == true && weight_passed == false)
        cout << "Rejected: Too heavy." << endl;
    else if (dimensions_passed == false && weight_passed == true)
        cout << "Rejected: Too big." << endl;
    else
        cout << "Accepted!" << endl;
    return 0;
}

Answer 1

You need to initialize your variables, particularly your bool in this case

bool weight_passed = true;
bool dimensions_passed = true;

Answer 2

What is weight_passed if weight < 27 ? And what is dimensions_passed , if dimensions < 0.1 ? They are not assigned to--and so are indeterminate. You need to initialize them like so:

bool weight_passed = true;
bool dimensions_passed = true;

You can do that at the declaration, or in main() .

Alternatively, you can put an else on your if s:

if (weight >= 27)
    weight_passed = false;
else
    weight_passed = true;

if (dimensions >= 0.1)
    dimensions_passed = false;
else
    dimensions_passed = true;

Since you're new, I'll give you some other tips. The part inside the parentheses of each if can be treated like a boolean. So you can do:

weight_passed = (weight < 27); // equivalent to !(weight >= 27)
dimensions_passed = (dimensions < 0.1); // equivalent to !(dimensions >= 0.1)

This will not only give you the same result, but will guarantee your variables are getting assigned.

Last thing: Since what goes into if conditions is boolean logic, you don't have to use those equality operators ( == ):

if (!dimensions_passed && !weight_passed)
    // BOTH too big AND too heavy. Geez, see a doctor man.
else if (dimensions_passed)
    // dimensions pass though, so must just be too heavy
else if (weight_passed)
    // weight_passed, so must just be too big
else
    // Goldilocks would say this one is just right.