When I enter the input, the c++ window just closes

Question

#include <bits/stdc++.h>

using namespace std;

struct Cow
{
    int p, s, t;
};

int main()
{
    int n, b;
    cin >> n >> b;

    Cow cows[n];

    for (int i = 0; i < n; i++)
    {
        cin >> cows[i].p >> cows[i].s;
        cows[i].t = cows[i].p + cows[i].s;
    }

    int temp = b;
    int best = 0;

    for (int i = 0; i < n; i++)
    {
        temp = b;
        int counter = 0;
        for (int j = 0; j < n; j++)
        {
            if (j == i)
            {
                temp = temp - (cows[j].p / 2 + cows[j].s);
            }
            else
            {
                temp = temp - cows[j].t;
            }
            if (temp < 0)
            {
                break;
            }
            else
            {
                counter++;
            }
            if (counter > best)
            {
                best = counter;
            }
        }

        cout << best;

        return 0;
    }

In the above code, when I run it, it opens up a window as usual, and let's me enter the input (shown below) fine as well.

5 24
4 2
2 0
8 1
6 3
12 5

But when I press enter, it just loads for a couple of seconds, then closes the C++ window. Any help?

Thanks in advance!

Answer 1

It's a common problem when you run your program from the IDE, as the program ends the window automatically closes, to prevent this you can do as follows:

//...
cout << best;

cin.get(); //get the newline character present in the buffer from previous cin
cin.get(); //wait for the user to hit enter before closing the window (if needed)

return 0;
//...

You are also missing a bracket, since your program runs I assume you just missed it when you posted the code, you should include it exactly like in your code for a more complete diagnostic.

---

Side notes:

---

1. Variable Length Arrays (cows[n]) are not part of C++ standard, though some compilers allow it, you shouldn't use it. Try std::vector.

Why aren't variable-length arrays part of the C++ standard?

---

2. Don't use #include <bits/stdc++.h>, it's a bad practice, moreover in this case where you only need the <iostream> library.

Why should I not #include <bits/stdc++.h>?

---

3. using namespace std; is also not good. Use std:: scope or individual usings, for instance: using std::cout;

Why is "using namespace std;" considered bad practice?

---

The combination of 2 and 3 can sometimes have nasty effects.

Consider the following example:

#include <bits/stdc++.h>

using namespace std;

int size = 0;

int main()
{
    cout << size;
}

This code works fine with pre C++17 compilers, but since C++17 introduced std::size, you will have an ambiguous reference to size and your program will fail to compile.

Credits for the example to @user4581301.

Answer 2

In the code you pasted, the "return 0" instruction is placed in the for "i" loop.

If it is the same in your file, it will automatically end on the first run of this loop, with only one "cout".

Answer 3

In some quick debugging, here are a few issues I've found with your code.

Line 14:

Cow cows[n];

According to most C++ compilers, arrays are static in memory, what this means is you have to make an array of constant size. An array cannot be declared of variable length.

Even if the compiler you use supports this feature, it's bad practice. Look instead into std::vector, like other users have said.

Line 26:

counter = 0;

You have to declare counter's type before you initialize a value to it.

Something like:

int counter = 0;

Line 47:

return 0;

This is the reason the window closes prematurely. This command effectively ends a main function, and it is currently being run inside of a for loop.
In the first iteration of the for loop, the program will end and your loop will end prematurely.

You should move the return statement out of the for loop, then add an ending closing curly brace '}' to close off your main function.