C++ fundamentals · Lesson 5 of 21

Loops

for, while and do-while, break and continue, and nested loops.

10 minutes3 games

for when you know how many times. It has three parts: start, condition and step. while when repetition depends on a condition (like "until the number reaches zero").

C++

#include <iostream>

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

    int n = 4096, steps = 0;
    while (n > 1) {
        n /= 2;
        steps++;
    }
    std::cout << "halved " << steps << " times\n";
    return 0;
}

Step by step1 / 8

▶int sum = 0;
2for (int i = 1; i <= 4; i++) {
3 sum += i;
4}
5std::cout << sum;

Variables

sum

Output

…

Follow i and sum on each pass.

break leaves the loop entirely; continue skips the rest of the current pass. do { } while (…) runs at least once before testing its condition.

C++

#include <iostream>

int main() {
    // Nested loops: a small multiplication table
    for (int r = 1; r <= 3; r++) {
        for (int c = 1; c <= 4; c++) {
            std::cout << r * c << "\t";
        }
        std::cout << "\n";
    }

    // First multiple of 7 above 50, skipping odd numbers
    for (int x = 51; ; x++) {
        if (x % 2 != 0) continue;
        if (x % 7 == 0) {
            std::cout << "found " << x << "\n";
            break;
        }
    }
    return 0;
}

What's the output?

#include <iostream>
int main() {
    int count = 0;
    for (int i = 0; i < 10; i += 3) {
        count++;
    }
    std::cout << count << "\n";
}

What will this code print?

Order the lines

Order the code that prints the even numbers from 2 to 10.

Click the lines in the right order

Exercise

Print the sum of the numbers from 1 to 100 that are divisible by 3 or 5.

Expected output: 2418

C++

#include <iostream>

int main() {
    int sum = 0;
    
    std::cout << sum << "\n";
    return 0;
}

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