Chapter 1 Exercises¶

Work through these after reading Chapter 1. Try each one yourself before revealing the solution — you learn far more from an honest attempt, and the mistakes along the way, than from reading a finished program. Type the code into CLion and run it; do not just read it.

When you open a solution it appears blurred — click it once more to reveal it, so you do not see the answer by accident.

Where to put your code¶

Each exercise is its own small program with its own main(), and a CLion project runs one main() at a time. You have two options:

Simplest — keep one project open and replace the contents of main.cpp for each exercise. Run it, then paste in the next. (You lose the previous attempt, which is fine for quick practice.)

Keeps every exercise (recommended) — give each exercise its own file in a single project (ex1.cpp, ex2.cpp, …) and add one line per file to CMakeLists.txt:

add_executable(ex1 ex1.cpp)
add_executable(ex2 ex2.cpp)

Then choose which program to run from the run-configuration dropdown next to the green ▶ button. You do not need to understand CMakeLists.txt yet — CMake explains it in Chapter 2; for now, just copy the pattern.

1. Introduce yourself¶

Practises: Basic Structure, Variables and Basic Types

Declare a std::string for your name and an int for your age (just like the chapter's int age = 25). Print one line:

My name is Ada and I am 36 years old.

Show solution

#include <iostream>
#include <string>

int main() {
    std::string name = "Ada";
    int age = 36;

    std::cout << "My name is " << name << " and I am " << age << " years old.\n";
}

Each variable gets the right type and is initialised as it is declared; << chains the pieces into one line.

2. Average score¶

Practises: Operators and Expressions

You have three test scores: 7, 8, and 10. Print their average. Make sure it comes out as a decimal — 8.33…, not a truncated 8.

Show solution

#include <iostream>

int main() {
    int a = 7;
    int b = 8;
    int c = 10;

    double average = (a + b + c) / 3.0;   // 3.0 is a double, so the decimals are kept

    std::cout << "Average: " << average << "\n";
}

Divide by 3 (an int) and C++ does integer division — it throws the fraction away and you get 8. Writing 3.0 makes one side a double, so the decimals survive. That is the chapter's 10 / 3 rule in action.

3. Sensor readings¶

Practises: Strings and Vectors, Control Statements

Store five sensor readings — 42, 17, 99, 8, 56 — in a std::vector<int>. Print how many there are, their average (as a decimal), and the largest.

Hint: loop over the vector to add up the values and track the biggest; readings.size() is the count.

Show solution

#include <iostream>
#include <vector>

int main() {
    std::vector<int> readings = {42, 17, 99, 8, 56};

    int sum = 0;
    int largest = readings[0];
    for (int r : readings) {
        sum += r;
        if (r > largest) {
            largest = r;
        }
    }

    double average = static_cast<double>(sum) / readings.size();

    std::cout << "Count:   " << readings.size() << "\n";
    std::cout << "Average: " << average << "\n";
    std::cout << "Largest: " << largest << "\n";
}

A range-based for visits every element: we add each to sum and keep the biggest seen so far. static_cast<double> keeps the division decimal (the integer-division rule again), and readings.size() gives the element count.

4. Even or odd¶

Practises: Control Statements

Use a for loop to print the numbers 1 to 10, labelling each one even or odd.

Hint: a number is even when n % 2 == 0.

Show solution

#include <iostream>

int main() {
    for (int i = 1; i <= 10; ++i) {
        if (i % 2 == 0) {
            std::cout << i << " even\n";
        } else {
            std::cout << i << " odd\n";
        }
    }
}

A counter-based for loop like the one in the chapter, with an if/else inside it deciding what to print.

5. Squares¶

Practises: Functions

Write a function int square(int n) that returns n * n (you saw this exact function in the chapter). Then use a for loop to print the squares of 1 through 5.

Show solution

#include <iostream>

int square(int n) {
    return n * n;
}

int main() {
    for (int i = 1; i <= 5; ++i) {
        std::cout << i << " squared is " << square(i) << "\n";
    }
}

A small function with one clear job, called from a loop. Defining square once and reusing it beats writing i * i everywhere.

6. Traffic light¶

Practises: Enumerations

Define an enum class TrafficLight with Red, Amber, and Green. Write a function that prints the action for each — Stop, Get ready, Go — using a switch, and call it for all three.

Show solution

#include <iostream>

enum class TrafficLight {
    Red,
    Amber,
    Green
};

void act(TrafficLight light) {
    switch (light) {
        case TrafficLight::Red:   std::cout << "Stop\n";      break;
        case TrafficLight::Amber: std::cout << "Get ready\n"; break;
        case TrafficLight::Green: std::cout << "Go\n";        break;
    }
}

int main() {
    act(TrafficLight::Red);
    act(TrafficLight::Amber);
    act(TrafficLight::Green);
}

A fixed set of named values handled by a switch. With no default, the compiler warns you if you add a colour later and forget it here.

7. Keep asking¶

Practises: Control Statements

Ask the user for a positive number, over and over, until they actually give you one. Then print it. Use a do-while loop, so you ask at least once.

Hint: this is the do-while pattern from the chapter — read inside the loop, and repeat while the value is not yet positive.

Run it — you should see:

Enter a positive number: -4
Enter a positive number: 0
Enter a positive number: 12
Thanks — you entered 12

Show solution

#include <iostream>

int main() {
    int number = 0;

    do {
        std::cout << "Enter a positive number: ";
        std::cin >> number;
    } while (number <= 0);

    std::cout << "Thanks — you entered " << number << "\n";
}

A do-while runs its body before testing the condition, so the prompt always appears at least once. The loop repeats as long as number <= 0, so it only lets you out once the value is genuinely positive — exactly what "keep asking until it is valid" needs.

8. Greet by full name¶

Practises: Strings and Vectors

Ask for the user's full name (first and last, with the space), greet them, and report how many characters the name has. Because the name contains a space, you need std::getline, not std::cin >>.

Hint: std::getline(std::cin, name) reads the whole line; name.length() counts its characters.

Run it — you should see:

Enter your full name: Ada Lovelace
Hello, Ada Lovelace
Your name has 12 characters.

Show solution

#include <iostream>
#include <string>

int main() {
    std::string name;

    std::cout << "Enter your full name: ";
    std::getline(std::cin, name);

    std::cout << "Hello, " << name << "\n";
    std::cout << "Your name has " << name.length() << " characters.\n";
}

std::getline reads the entire line, spaces included, so Ada Lovelace arrives whole — std::cin >> name would have stopped at the space and kept only Ada. The count of 12 includes the space, because it is one of the characters in the string.

9. Temperature classifier¶

Practises: Control Statements

Read a temperature (a whole number of degrees Celsius) and print a description using an if / else if / else chain: below 0 is Freezing, 0 to 14 is Cold, 15 to 24 is Comfortable, and 25 or above is Hot.

Hint: test the coldest case first and work upward, so each else if only has to check its upper bound.

Run it — you should see:

Enter the temperature in Celsius: 18
Comfortable

Show solution

#include <iostream>

int main() {
    int celsius = 0;

    std::cout << "Enter the temperature in Celsius: ";
    std::cin >> celsius;

    if (celsius < 0) {
        std::cout << "Freezing\n";
    } else if (celsius < 15) {
        std::cout << "Cold\n";
    } else if (celsius < 25) {
        std::cout << "Comfortable\n";
    } else {
        std::cout << "Hot\n";
    }
}

Only the first matching branch runs, so ordering the tests from coldest upward lets each else if assume everything below it was already ruled out: by the time celsius < 15 is checked, we know it is not below 0, so that branch means 0 to 14. The final else catches everything left — 25 and above.