Rust median, mean and mode

main.rs

use std::collections::HashMap;

fn main () {
    let mut numbers = vec![12, 14, 8, 3, 5, 19, 23, 24, 28, 32, 48, 13, 13, 48];

    println!("median is {}", median(&mut numbers));
    println!("mean is {}", mean(&numbers));
    println!("mode is {}", mode(&numbers));
}

fn median(numbers: &mut [i32]) -> f64 {
    numbers.sort();

    let middle = numbers.len() / 2;

    match numbers.len() % 2 {
        0 => (numbers[middle] + numbers[middle - 1]) as f64 / 2.0,
        _ => numbers[middle] as f64,
    }
}

fn mean(numbers: &[i32]) -> f64 {
    let sum: i32 = numbers.iter().sum();
    sum as f64 / numbers.len() as f64
}

fn mode(numbers: &[i32]) -> i32 {
    let mut occurrences = HashMap::with_capacity(numbers.len());

    for number in numbers {
        let count = occurrences.entry(number).or_insert(0);
        *count += 1;
    }

    let max_value = occurrences.values().map(|v| *v).max().unwrap();

    let mut modes = occurrences
        .into_iter()
        .filter_map(|(k, v)| if v == max_value { Some(*k) } else { None })
        .collect::<Vec<i32>>();

    // By convention, we return the mode with the smallest value
    modes.sort();
    modes[0]
}