Rust Practice Exercises

Palindrome Check in Rust

Does the text read the same in both directions? Ignore spaces, punctuation and case.

Beginner
2 min read
1 runnable example

What you'll learn

Filtering letters
Lower case
Comparing with the reverse

Run code →

level

The first and last letters match, then the next pair.

The same forwards and backwards

A palindrome reads the same in both directions, such as level. A good check ignores spaces, punctuation and the difference between upper and lower case.

filter keeps only letters and digits and map makes them lower case. eq compares the letters with the same letters in reverse order, without building a second vector. {text:?} prints the text with quotes.

Key points

Keep only letters and digits.
Compare in lower case.
eq compares two iterators item by item.

Runnable Rust example

Rust

Run code →

main.rs

fn is_palindrome(text: &str) -> bool {
    let letters: Vec<char> = text
        .chars()
        .filter(|c| c.is_alphanumeric())
        .map(|c| c.to_ascii_lowercase())
        .collect();
    letters.iter().eq(letters.iter().rev())
}

fn main() {
    for text in ["level", "A man, a plan, a canal: Panama", "Rust"] {
        println!("{text:?} -> {}", is_palindrome(text));
    }
}

Get a Run button for this example Result of running the code

"level" -> true
"A man, a plan, a canal: Panama" -> true
"Rust" -> false

Practice

Open the example in the online compiler, change a value or add a line, and predict the output before you run it. Then break the code on purpose and read the compiler's message.

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Next: Word Frequency Counter →

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