Question

please, Answer all questions and give a detailed explanation.

What is output by the following? class A public: AO { ++x; } static int x; int A::X - 1; int maino vector<A> vec(8): cout << A: :: 11111111 1111111111 What is output by the following? class A public: AO ++ ; } AO ( X ) static int x: int A::: int maino vector<A vec(5): 1 (Alix < 10) Ab, c, d, e, fg: cout < vec.at (2).X: VINNA

Answer 1

Answer 1:

OUTPUT:

2

CODE (WITH COMMENTS):

#include <iostream>

#include <vector>

using namespace std;

class A{

public:

    A() { ++x; } // Constructor which increments x everytime a new object of A is created

    static int x; // static variable is common accross all objects of A

};

int A::x = 1; // Initialize x with 1

int main(){

    vector<A> vec(8);   // Reserves memory for 8 elements of type A and calls constructor of A only once

                        // to initialize all 8 objects and then after initialization destructor is called.

    cout << A::x; // Since, constructor has been called only once, therefore, A::x = 2 at this point of time

    return 0;

}

Answer 2:

OUTPUT:

1

CODE (WITH COMMENTS):

#include <iostream>

#include <vector>

using namespace std;

class A{

public:

    A() { ++x; } // Constructor which increments x everytime a new object of A is created

    ~A() { --x; } // Destructor which decrements x everytime an object goes out of scope

    static int x; // static variable is common accross all objects of A

};

int A::x = 1; // Initialize x with 1

int main(){

    vector<A> vec(5);   // Reserves memory for 5 elements of type A and calls constructor of A only once

                        // to initialize all 5 objects and then after initialization destructor is called.

    // Since, constructor and destructor have been called once, therefore, x remains 1 at this point of time

    

    // A::x < 10 is true because A::x = 1

    if (A::x < 10){

        A b, c, d, e, f, g; // Creates 6 objects of A and A::x becomes 1 + 6 = 7. These objects are local to

                            // this if block only and will be destroyed once goes out of the if block.

    }

    // Here, above 6 objects created goes out of scope therefore destructor will be called for each object

    // and A::x will be decremented 6 times in total. Hence, A::x will become 7 - 6 = 2 at this point of time.

    cout << vec.at(2).x; // vec.at(2).x is same as A::x. Therefore, 1 will be printed here.

    return 0;

}

Answer 3:

OUTPUT:

15

CODE (WITH COMMENTS):

#include <iostream>

#include <vector>

using namespace std;

struct X{

    // Constructor to initialize this->a = _a and this->b = b

    X(int _a, int b) : a(_a), b(b) {}

    int a, b;

};

int main(){

    X myX(1, 5); // Create object of struct with myX.a = 1 and myX.b = 5

    cout << myX.a << myX.b; // Here, myX.a = 1 and myX.b = 5. So, 15 will be printed

    return 0;

}

Answer 4:

OUTPUT:

welp

CODE (WITH COMMENTS):

#include <iostream>

#include <string>

using namespace std;

// This function takes a reference to the string object and an integer value

// and returns a reference to the character stored at i-th index in the string s.

// Reference to ith character is returned so that character can be changed by callee function

char& GetChar(string& s, int i){

    return s.at(i);

}

int main(){

    string message = "Help"; // Here, message[0] = 'H', message[1] = 'e', message[2] = 'l', and message[3] = 'p'

    GetChar(message, 0) = 'w'; // GetChar returns refernce to message[0] and then message[0] = 'w' is done

    // Therefore, message[0] = 'w', message[1] = 'e', message[2] = 'l', and message[3] = 'p'

    // message becomes "welp"

    cout << message; // Prints "welp"

    return 0;

}