OOPs PYQs practice

Author: Tamoziit

practice/p1.cpp

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+#include <iostream>
+using namespace std;
+
+void updateByReference(int &x)
+{
+    cout << &x << " : " << x << endl;
+    x += 10;
+}
+
+void updateByAddress(int *x)
+{
+    cout << x << " : " << *x << endl;
+    *x += 10;
+}
+
+int main()
+{
+    int a = 5;
+    updateByReference(a);
+    cout << "a after updateByReference: " << a << endl;
+    updateByAddress(&a);
+    cout << "a after updateByAddress: " << a << endl;
+    return 0;
+}

practice/p10.java

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+
+//package practice;
+import java.util.*;
+
+public class p10 {
+    void sort(int[] args) {
+        int i, j, temp;
+        for (i = 0; i < args.length - 1; i++) {
+            for (j = 0; j < args.length - i - 1; j++) {
+                if (args[j] > args[j + 1]) {
+                    temp = args[j];
+                    args[j] = args[j + 1];
+                    args[j + 1] = temp;
+                }
+            }
+        }
+    }
+
+    void display(int[] args) {
+        int i;
+        for (i = 0; i < args.length; i++) {
+            System.out.print(args[i] + " ");
+        }
+        System.out.println();
+    }
+
+    public static void main(String[] args) {
+        p10 ob = new p10();
+        int i;
+        int[] arr = new int[5];
+        for (i = 0; i < 5; i++) {
+            arr[i] = Integer.valueOf(args[i]);
+        }
+
+        ob.display(arr);
+        ob.sort(arr);
+        System.out.println("Sorted args:");
+        ob.display(arr);
+    }
+}

practice/p11.cpp

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+#include <iostream>
+using namespace std;
+
+class Test
+{
+public:
+    int i;
+
+    Test(int idx)
+    {
+        i = idx;
+        cout << "Object Created: " << i << endl;
+    }
+
+    ~Test()
+    {
+        cout << "Object Destroyed: " << i << endl;
+    }
+};
+
+int main()
+{
+    Test t1(1);
+    Test t2(2);
+    return 0;
+}

practice/p12.java

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+class Department {
+    Department() {
+        System.out.println("CSE");
+    }
+
+    Department(String name) {
+        this();
+        System.out.println("CSE: String Constructor" + name);
+    }
+}
+
+public class p12 extends Department {
+    p12() {
+        System.out.println("Third year ");
+    }
+
+    p12(String name) {
+        this();
+        System.out.println("Third year: String Constructor" + name);
+    }
+
+    public static void main(String[] args) {
+        new p12("Section A+B+C");
+    }
+}

practice/p2.cpp

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+#include <iostream>
+using namespace std;
+
+void printVal(void *ptr)
+{
+    cout << "Value = " << *(int *)ptr << endl;
+}
+
+int main()
+{
+    int a = 7;
+    printVal((int *)&a);
+    return 0;
+}

practice/p3.cpp

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+#include <iostream>
+using namespace std;
+
+class test
+{
+public:
+    test() { cout << "Cons" << endl; }
+    ~test() { cout << "Dest" << endl; }
+};
+
+int main()
+{
+    for (int i = 0; i < 2; i++)
+        test obj;
+    return 0;
+}

practice/p4.cpp

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+#include <iostream>
+using namespace std;
+
+class MyClass
+{
+private:
+    static int count; // static variable to track number of objects
+
+public:
+    // Constructor
+    MyClass()
+    {
+        count++;
+        cout << "Object created. Total alive: " << count << endl;
+    }
+
+    // Destructor
+    ~MyClass()
+    {
+        count--;
+        cout << "Object destroyed. Total alive: " << count << endl;
+    }
+
+    // Static function to access count
+    static int getCount()
+    {
+        return count;
+    }
+};
+
+// Initialize static variable outside the class
+int MyClass::count = 0;
+
+int main()
+{
+    MyClass obj1;
+    {
+        MyClass obj2, obj3;
+        cout << "Currently alive: " << MyClass::getCount() << endl;
+    } // obj2 and obj3 go out of scope here
+
+    cout << "Currently alive after block: " << MyClass::getCount() << endl;
+
+    return 0;
+}

practice/p5.java

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+public class p5 {
+    public static void main(String[] args) {
+        int i;
+        System.out.println("Command Line Args:");
+        for (i = 0; i < args.length; i++) {
+            System.out.print(args[i] + " ");
+        }
+
+        System.out.println();
+    }
+}

practice/p6.java

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+//package practice;
+
+public class p6 {
+    double getArea(int r) {
+        return (22.0 / 7.0) * r * r;
+    }
+
+    double getArea(int l, int b) {
+        return l * b;
+    }
+
+    public static void main(String[] args) {
+        p6 ob = new p6();
+        System.out.println("Area of Circle  = " + ob.getArea(7));
+        System.out.println("Area of Rectangle  = " + ob.getArea(3, 4));
+    }
+}

practice/p7.cpp

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+#include <iostream>
+using namespace std;
+
+class Animal {
+public:
+    virtual void sound() { // virtual method
+        cout << "Animal makes a sound" << endl;
+    }
+};
+
+class Animal2 {
+public:
+    void sound() { // non-virtual method
+        cout << "Animal makes a sound in 2" << endl;
+    }
+};
+
+class Dog : public Animal {
+public:
+    void sound() override {
+        cout << "Dog barks" << endl;
+    }
+};
+
+class Dog2 : public Animal2 {
+public:
+    void sound() {
+        cout << "Dog barks 2" << endl;
+    }
+};
+
+int main() {
+    Animal* a;
+    Animal2* b;
+    Dog d;
+    Dog2 d2;
+    a = &d;
+    a->sound(); // Resolved at runtime
+    b = &d2;
+    b->sound();
+    return 0;
+}

practice/p8.cpp

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+#include <iostream>
+using namespace std;
+
+int main() {
+    void *ptr;
+    int x = 6;
+    ptr = &x;
+
+    // Print int
+    cout << "Value of x: " << *((int *)ptr) << endl;
+
+    // Reassign ptr to a char array
+    char str[] = "Hello, world!";
+    ptr = str; // now ptr points to char array
+
+    // Print char array
+    cout << "Character array: " << (char *)ptr << endl;
+
+    return 0;
+}

practice/p9.cpp

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+#include <iostream>
+using namespace std;
+
+class test
+{
+    int var;
+
+public:
+    test()
+    {
+        var = 0;
+        cout << var << endl;
+    }
+    test(int a)
+    {
+        var = a;
+        cout << var << endl;
+    }
+};
+
+int main()
+{
+    test obj;
+}