Nesting and combining control structures in C++

In C++, control structures can be nested and combined to create more complex and flexible programs. Here are some examples of how control structures can be nested and combined:

1. Nesting if statements: If statements can be nested to create multiple levels of conditions. For example:

int x = 10;
if (x > 0) {
    if (x < 100) {
        cout << "x is between 0 and 100" << endl;
    } else {
        cout << "x is greater than or equal to 100" << endl;
    }
} else {
    cout << "x is non-positive" << endl;
}

In this example, the first if statement checks if `x` is positive, and if it is, the second if statement checks if `x` is less than 100.

2. Combining if-else and for loops: If-else statements can be combined with for loops to create more complex programs. For example:

for (int i = 1; i <= 10; i++) {
    if (i % 2 == 0) {
        cout << i << " is even" << endl;
    } else {
        cout << i << " is odd" << endl;
    }
}

In this example, the for loop iterates over the numbers from 1 to 10, and the if-else statement checks if each number is even or odd.

3. Nesting loops: Loops can also be nested to create more complex programs. For example:

for (int i = 0; i < 5; i++) {
    for (int j = 0; j < 5; j++) {
        cout << i << "," << j << " ";
    }
    cout << endl;
}

In this example, the outer for loop iterates over the values of `i` from 0 to 4, and the inner for loop iterates over the values of `j` from 0 to 4 for each value of `i`. The cout statement inside the inner loop prints the values of `i` and `j`.

4. Combining switch and for loops: Switch statements can also be combined with for loops to create more complex programs. For example:

for (int i = 1; i <= 5; i++) {
    switch (i) {
        case 1:
        case 2:
            cout << i << " is a small number" << endl;
            break;
        case 3:
        case 4:
            cout << i << " is a medium number" << endl;
            break;
        case 5:
            cout << i << " is a large number" << endl;
            break;
        default:
            cout << "Invalid number" << endl;
            break;
    }
}

In this example, the for loopiterates over the values of `i` from 1 to 5, and the switch statement checks if each value of `i` falls into the category of small, medium, or large numbers.

By nesting and combining control structures in C++, you can create more complex and flexible programs that can handle a wider range of situations and conditions. However, it is important to keep in mind that overly complex code can be difficult to read and maintain, so it is important to balance the need for complexity with the need for readability and maintainability.