Array not producing correct output - c++

Question

I have a problem with assigning variables to an array from different functions. I have two functions that produce different numbers. I then want to assign those numbers to a private array in the same class. When I do this the array returns large negative numbers.
// Array.h
class Array {
private:
int W = A;
int Q = B;
int sum[2] = {W, Q};
public:
int A;
int B;
int num1();
int num2();
int add();
};
// Array.cpp
#include<iostream>
using namespace std;
#include "Array.h"
int Array::num1()
{
int x = 3;
int y = 4;
A = x + y;
cout << A << endl;
return A;
}
int Array::num2()
{
int x = 2;
int y = 5;
B = x + y;
cout << B << endl;
return B;
}
int Array::add()
{
for(int i = 0; i < 2; i++)
{
cout << sum[i] << endl;
}
return 0;
}
// main.cpp
#include <iostream>
#include "Array.h"
int main() {
Array sumTotal;
sumTotal.num1();
sumTotal.num2();
sumTotal.add();
return 0;
}

Answer 1

Problem is here:
int W = A;
int Q = B;
int sum[2] = { W, Q };
You are just coping value from A and B to W and Q.
And later when you set A and B, those changes are not reflected to W or Q.
Thus leaving W and Q uninitialized.
Note: consider researching more about C++ topic in field of arrays, pointers and references.
This is modified code that works ok:
#include <iostream>
using namespace std;
class Array {
private:
int sum[2];
public:
int num1();
int num2();
int add();
};
int Array::num1()
{
int x = 3;
int y = 4;
sum[0] = x + y;
cout << sum[0] << endl;
return sum[0];
}
int Array::num2()
{
int x = 2;
int y = 5;
sum[1] = x + y;
cout << sum[1] << endl;
return sum[1];
}
int Array::add()
{
for (int i = 0; i < 2; i++)
{
cout << sum[i] << endl;
}
return 0;
}
int main(int argc, char** argv)
{
Array sumTotal;
sumTotal.num1();
sumTotal.num2();
sumTotal.add();
return 0;
}

Answer 2

The reason you are getting garbage values (large negative numbers, in your case) is that you are not initializing A or B to any meaningful values, and then you are not updating sum when you call num1, or num2.
You should initialize A and B to something meaningful in the class, or at least default initialize it.
Then you need to update sum in num1, like this:
int Array::num1()
{
int x = 3;
int y = 4;
A = x + y;
sum[0] = A; // <- add this
cout << A << endl;
return A;
}
and do a similar thing inside num2.
You also have 2 variables W, and Q inside your class which don't seem to serve any purpose. Apart from the issue with initializing them incorrectly with garbage values, you don't even need them; you could just use A, and B instead.