Rust Practice Exercises

Sort Structs in Rust: Student Ranking

Sort a vector of structs by score and name with sort_by, then compute the average.

Beginner
3 min read
1 runnable example

What you'll learn

sort_by with a closure
then for tie breaks
Average with iterators

Run code →

Ranking

Leo95

Mia82

Zoe82

Ben67

Mia comes before Zoe because the scores are equal.

Sort by score, then by name

Real data is usually a list of records. Sort the students by score from high to low, break ties by name, and print the ranking.

sort_by takes a closure that compares two students. b.score.cmp(&a.score) sorts from high to low, and then falls back to the name when the scores are equal. The average converts the sum to f64 so the division keeps its fraction.

Key points

b.cmp(a) sorts from high to low.
then breaks ties by name.
Convert to f64 before dividing.

Runnable Rust example

Rust

Run code →

main.rs

struct Student {
    name: &'static str,
    score: u32,
}

fn main() {
    let mut students = vec![
        Student { name: "Mia", score: 82 },
        Student { name: "Leo", score: 95 },
        Student { name: "Zoe", score: 82 },
        Student { name: "Ben", score: 67 },
    ];

    students.sort_by(|a, b| b.score.cmp(&a.score).then(a.name.cmp(b.name)));
    for (rank, student) in students.iter().enumerate() {
        println!("{}. {} ({})", rank + 1, student.name, student.score);
    }

    let average = students.iter().map(|s| s.score).sum::<u32>() as f64 / students.len() as f64;
    println!("average: {average:.1}");
}

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

1. Leo (95)
2. Mia (82)
3. Zoe (82)
4. Ben (67)
average: 81.5

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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