Loop with break in Rust - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a loop with break returning a value

What is the output of this Rust program?

Rust

fn main() {
    let mut count = 0;
    let result = loop {
        count += 1;
        if count == 5 {
            break count * 2;
        }
    };
    println!("{}", result);
}

A 0

B 5

C 10

D Compilation error

💡 Hint

The loop breaks when count reaches 5 and returns count * 2.

The loop increments count from 0 to 5. When count is 5, it breaks and returns 5 * 2 = 10. This value is stored in result and printed.

❓ Predict Output

intermediate

Loop with break inside nested loops

What will be printed by this Rust code?

Rust

fn main() {
    let mut i = 0;
    let mut j = 0;
    'outer: loop {
        i += 1;
        loop {
            j += 1;
            if j == 3 {
                break 'outer;
            }
        }
    }
    println!("i = {}, j = {}", i, j);
}

A Compilation error

B i = 3, j = 3

C i = 1, j = 1

D i = 1, j = 3

💡 Hint

The break with label exits the outer loop when j reaches 3.

The inner loop increments j until it reaches 3, then breaks the outer loop. i was incremented once before entering inner loop, so i=1 and j=3.

🔧 Debug

advanced

Identify the error in loop with break

What error does this Rust code produce?

Rust

fn main() {
    let mut x = 0;
    let y = loop {
        x += 1;
        if x > 3 {
            break x;
        }
    };
    println!("{}", y);
}

A SyntaxError: missing semicolon after x += 1

B TypeError: cannot break with a value

C No error, prints 4

D RuntimeError: infinite loop

💡 Hint

Check punctuation carefully inside the loop.

The line 'x += 1' is missing a semicolon, causing a syntax error.

❓ Predict Output

advanced

Loop with break returning a tuple

What is the output of this Rust program?

Rust

fn main() {
    let mut a = 0;
    let mut b = 1;
    let result = loop {
        if a > 3 {
            break (a, b);
        }
        a += 1;
        b += 2;
    };
    println!("{:?}", result);
}

A (3, 7)

B (4, 9)

C (4, 5)

D Compilation error

💡 Hint

The loop breaks when a becomes greater than 3, returning (a, b).

a increments from 0 to 4, b increments by 2 each time from 1 to 9. When a is 4 (>3), loop breaks returning (4,9).

🧠 Conceptual

expert

Behavior of break in infinite loop with condition

Consider this Rust code snippet: fn main() { let mut n = 0; loop { n += 1; if n == 10 { break; } } println!("{}", n); } What is the value printed and why?

A 10, because the loop breaks exactly when n reaches 10

B 9, because the break happens before incrementing n to 10

C Compilation error due to missing break value

D Infinite loop, because break has no value

💡 Hint

The break without a value just exits the loop; n increments before the check.

n starts at 0, increments to 10, then break exits the loop. The printed value is 10.