C++ Basics

#include <iostream>
using namespace std;

int main() {
    cout << "Hello, World!" << endl;
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    // Integer types
    int age = 25;
    short year = 2024;
    long population = 7800000000L;
    
    // Floating point types
    float height = 5.9f;
    double pi = 3.14159265359;
    
    // Character and boolean
    char grade = 'A';
    bool isStudent = true;
    
    // Display values
    cout << "Age: " << age << endl;
    cout << "Height: " << height << endl;
    cout << "Pi: " << pi << endl;
    cout << "Grade: " << grade << endl;
    cout << "Is Student: " << isStudent << endl;
    
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    // Variable declaration and initialization
    int score = 95;
    double temperature = 98.6;
    char initial = 'J';
    bool isPassed = true;
    
    // Multiple variable declaration
    int x = 10, y = 20, z = 30;
    
    // Variable modification
    score = score + 5;  // score is now 100
    temperature *= 1.1; // temperature is now 108.46
    
    // Display variables
    cout << "Score: " << score << endl;
    cout << "Temperature: " << temperature << endl;
    cout << "Initial: " << initial << endl;
    cout << "Passed: " << (isPassed ? "Yes" : "No") << endl;
    
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    // Basic output
    cout << "Hello World!" << endl;
    
    // Output variables
    int age = 25;
    string name = "Alice";
    cout << "Name: " << name << ", Age: " << age << endl;
    
    // Multiple outputs in one line
    cout << "The answer is: " << 42 << endl;
    
    // Output without newline
    cout << "This ";
    cout << "is ";
    cout << "one line." << endl;
    
    return 0;
}

#include <iostream>
#include <string>
using namespace std;

int main() {
    // Reading different data types
    string name;
    int age;
    double height;
    
    // Get user input
    cout << "Enter your name: ";
    getline(cin, name);  // Use getline for strings with spaces
    
    cout << "Enter your age: ";
    cin >> age;
    
    cout << "Enter your height (in meters): ";
    cin >> height;
    
    // Display the information
    cout << "\n--- User Information ---" << endl;
    cout << "Name: " << name << endl;
    cout << "Age: " << age << " years old" << endl;
    cout << "Height: " << height << " meters" << endl;
    
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    double num1, num2;
    char operation;
    
    cout << "=== Simple Calculator ===" << endl;
    cout << "Enter first number: ";
    cin >> num1;
    
    cout << "Enter operation (+, -, *, /): ";
    cin >> operation;
    
    cout << "Enter second number: ";
    cin >> num2;
    
    cout << "\nResult: ";
    switch(operation) {
        case '+':
            cout << num1 << " + " << num2 << " = " << (num1 + num2);
            break;
        case '-':
            cout << num1 << " - " << num2 << " = " << (num1 - num2);
            break;
        case '*':
            cout << num1 << " * " << num2 << " = " << (num1 * num2);
            break;
        case '/':
            if(num2 != 0) {
                cout << num1 << " / " << num2 << " = " << (num1 / num2);
            } else {
                cout << "Error: Division by zero!";
            }
            break;
        default:
            cout << "Error: Invalid operation!";
    }
    cout << endl;
    
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    int a = 10, b = 3;
    
    // Arithmetic operations
    cout << "a + b = " << (a + b) << endl;  // 13
    cout << "a - b = " << (a - b) << endl;  // 7
    cout << "a * b = " << (a * b) << endl;  // 30
    cout << "a / b = " << (a / b) << endl;  // 3
    cout << "a % b = " << (a % b) << endl;  // 1
    
    // Comparison operations
    cout << "a == b: " << (a == b) << endl;  // 0 (false)
    cout << "a > b: " << (a > b) << endl;    // 1 (true)
    
    // Logical operations
    bool x = true, y = false;
    cout << "x && y: " << (x && y) << endl;  // 0 (false)
    cout << "x || y: " << (x || y) << endl;  // 1 (true)
    cout << "!x: " << (!x) << endl;          // 0 (false)
    
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    int score = 85;
    
    // Simple if statement
    if (score >= 90) {
        cout << "Excellent!" << endl;
    }
    
    // if-else statement
    if (score >= 60) {
        cout << "You passed!" << endl;
    } else {
        cout << "You failed!" << endl;
    }
    
    // if-else if-else statement
    if (score >= 90) {
        cout << "Grade: A" << endl;
    } else if (score >= 80) {
        cout << "Grade: B" << endl;
    } else if (score >= 70) {
        cout << "Grade: C" << endl;
    } else if (score >= 60) {
        cout << "Grade: D" << endl;
    } else {
        cout << "Grade: F" << endl;
    }
    
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    char grade;
    cout << "Enter your grade (A, B, C, D, F): ";
    cin >> grade;
    
    switch(grade) {
        case 'A':
        case 'a':
            cout << "Excellent! You got 90-100%" << endl;
            break;
        case 'B':
        case 'b':
            cout << "Good! You got 80-89%" << endl;
            break;
        case 'C':
        case 'c':
            cout << "Average! You got 70-79%" << endl;
            break;
        case 'D':
        case 'd':
            cout << "Below Average! You got 60-69%" << endl;
            break;
        case 'F':
        case 'f':
            cout << "Failed! You got below 60%" << endl;
            break;
        default:
            cout << "Invalid grade entered!" << endl;
    }
    
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    // for loop example
    cout << "For loop (1 to 5):" << endl;
    for (int i = 1; i <= 5; i++) {
        cout << i << " ";
    }
    cout << endl << endl;
    
    // while loop example
    cout << "While loop (countdown from 5):" << endl;
    int count = 5;
    while (count > 0) {
        cout << count << " ";
        count--;
    }
    cout << "Blast off!" << endl << endl;
    
    // do-while loop example
    cout << "Do-while loop:" << endl;
    int num = 1;
    do {
        cout << "Number: " << num << endl;
        num++;
    } while (num <= 3);
    
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    // break example
    cout << "Numbers from 1 to 10, stopping at 6:" << endl;
    for (int i = 1; i <= 10; i++) {
        if (i == 6) {
            break;  // Exit the loop when i equals 6
        }
        cout << i << " ";
    }
    cout << endl << endl;
    
    // continue example
    cout << "Even numbers from 1 to 10:" << endl;
    for (int i = 1; i <= 10; i++) {
        if (i % 2 != 0) {
            continue;  // Skip odd numbers
        }
        cout << i << " ";
    }
    cout << endl << endl;
    
    // Nested loops example
    cout << "Multiplication table (3x3):" << endl;
    for (int i = 1; i <= 3; i++) {
        for (int j = 1; j <= 3; j++) {
            cout << i * j << "\t";
        }
        cout << endl;
    }
    
    return 0;
}

#include <iostream>
#include <string>
using namespace std;

// Function declarations (prototypes)
int add(int a, int b);
void greet(string name);
double calculateArea(double radius);
int factorial(int n);

int main() {
    // Function calls
    int result = add(5, 3);
    cout << "5 + 3 = " << result << endl;
    
    greet("Alice");
    
    double area = calculateArea(5.0);
    cout << "Area of circle with radius 5: " << area << endl;
    
    int fact = factorial(5);
    cout << "5! = " << fact << endl;
    
    return 0;
}

// Function definitions
int add(int a, int b) {
    return a + b;
}

void greet(string name) {
    cout << "Hello, " << name << "! Welcome to C++!" << endl;
}

double calculateArea(double radius) {
    const double PI = 3.14159;
    return PI * radius * radius;
}

int factorial(int n) {
    if (n <= 1) {
        return 1;
    }
    return n * factorial(n - 1);  // Recursive function
}

#include <iostream>
using namespace std;

// Pass by value
void incrementByValue(int x) {
    x++;  // Only the copy is modified
    cout << "Inside function (by value): " << x << endl;
}

// Pass by reference
void incrementByReference(int &x) {
    x++;  // The original variable is modified
    cout << "Inside function (by reference): " << x << endl;
}

// Function with default parameters
void printInfo(string name, int age = 0, string city = "Unknown") {
    cout << "Name: " << name << ", Age: " << age << ", City: " << city << endl;
}

int main() {
    int num = 5;
    
    cout << "Original value: " << num << endl;
    
    incrementByValue(num);
    cout << "After pass by value: " << num << endl;
    
    incrementByReference(num);
    cout << "After pass by reference: " << num << endl;
    
    cout << "\nDefault parameters example:" << endl;
    printInfo("Alice");
    printInfo("Bob", 25);
    printInfo("Charlie", 30, "New York");
    
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    // Array declaration and initialization
    int numbers[5] = {10, 20, 30, 40, 50};
    
    // Accessing array elements
    cout << "First number: " << numbers[0] << endl;
    cout << "Third number: " << numbers[2] << endl;
    
    // Array traversal using for loop
    cout << "All numbers: ";
    for (int i = 0; i < 5; i++) {
        cout << numbers[i] << " ";
    }
    cout << endl;
    
    return 0;
}

#include <iostream>
#include <string>
using namespace std;

int main() {
    // String declaration and initialization
    string greeting = "Hello, World!";
    string name = "Alice";
    string empty_string = "";
    
    // String concatenation
    string message = greeting + " My name is " + name;
    cout << message << endl;
    
    // String length
    cout << "Length of greeting: " << greeting.length() << endl;
    cout << "Size of name: " << name.size() << endl;
    
    // Accessing characters
    cout << "First character of name: " << name[0] << endl;
    cout << "Last character of name: " << name[name.length() - 1] << endl;
    
    // String methods
    string text = "C++ Programming";
    cout << "Original: " << text << endl;
    cout << "Substring (0,3): " << text.substr(0, 3) << endl;
    cout << "Find 'Program': " << text.find("Program") << endl;
    
    // String comparison
    string str1 = "apple";
    string str2 = "banana";
    if (str1 < str2) {
        cout << str1 << " comes before " << str2 << endl;
    }
    
    return 0;
}

#include <iostream>
using namespace std;

int main() {
    // Variable declaration
    int number = 42;
    double price = 19.99;
    
    // Pointer declaration and initialization
    int* numPtr = &number;      // Pointer to int
    double* pricePtr = &price;  // Pointer to double
    
    // Display values and addresses
    cout << "Value of number: " << number << endl;
    cout << "Address of number: " << &number << endl;
    cout << "Value stored in numPtr: " << numPtr << endl;
    cout << "Value pointed to by numPtr: " << *numPtr << endl;
    
    // Modifying value through pointer
    *numPtr = 100;
    cout << "\nAfter modifying through pointer:" << endl;
    cout << "Value of number: " << number << endl;
    cout << "Value pointed to by numPtr: " << *numPtr << endl;
    
    // Null pointer
    int* nullPtr = nullptr;
    if (nullPtr == nullptr) {
        cout << "\nnullPtr is a null pointer" << endl;
    }
    
    return 0;
}

#include <iostream>
using namespace std;

// Global constant
const double PI = 3.14159;

int main() {
    // Local constants
    const int MAX_SIZE = 100;
    const string COMPANY_NAME = "TechCorp";
    
    // Using constants
    double radius = 5.0;
    double area = PI * radius * radius;
    
    cout << "Company: " << COMPANY_NAME << endl;
    cout << "Maximum size: " << MAX_SIZE << endl;
    cout << "Area of circle: " << area << endl;
    
    // Constant pointers
    int value1 = 10, value2 = 20;
    
    const int* ptr1 = &value1;     // Pointer to constant int
    int* const ptr2 = &value2;     // Constant pointer to int
    const int* const ptr3 = &value1; // Constant pointer to constant int
    
    // *ptr1 = 15;  // Error: cannot modify value through ptr1
    // ptr2 = &value1;  // Error: cannot change ptr2's address
    
    cout << "Value pointed by ptr1: " << *ptr1 << endl;
    cout << "Value pointed by ptr2: " << *ptr2 << endl;
    
    return 0;
}

#include <iostream>
#include <string>
using namespace std;

// Structure definition
struct Student {
    string name;
    int age;
    double gpa;
    char grade;
};

// Structure for representing a point
struct Point {
    double x;
    double y;
};

int main() {
    // Creating and initializing structure variables
    Student student1;
    student1.name = "Alice Johnson";
    student1.age = 20;
    student1.gpa = 3.85;
    student1.grade = 'A';
    
    // Alternative initialization
    Student student2 = {"Bob Smith", 19, 3.45, 'B'};
    
    // Creating point structures
    Point p1 = {10.5, 20.3};
    Point p2 = {15.0, 25.7};
    
    // Accessing structure members
    cout << "=== Student Information ===" << endl;
    cout << "Student 1:" << endl;
    cout << "  Name: " << student1.name << endl;
    cout << "  Age: " << student1.age << " years" << endl;
    cout << "  GPA: " << student1.gpa << endl;
    cout << "  Grade: " << student1.grade << endl << endl;
    
    cout << "Student 2:" << endl;
    cout << "  Name: " << student2.name << endl;
    cout << "  Age: " << student2.age << " years" << endl;
    cout << "  GPA: " << student2.gpa << endl;
    cout << "  Grade: " << student2.grade << endl << endl;
    
    // Working with point structures
    cout << "=== Point Coordinates ===" << endl;
    cout << "Point 1: (" << p1.x << ", " << p1.y << ")" << endl;
    cout << "Point 2: (" << p2.x << ", " << p2.y << ")" << endl;
    
    // Calculate distance between points
    double dx = p2.x - p1.x;
    double dy = p2.y - p1.y;
    double distance = sqrt(dx*dx + dy*dy);
    cout << "Distance between points: " << distance << endl;
    
    return 0;
}