rust_exercise.rs

use std::collections::HashMap;

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn it_works() {
        let ints = vec![1, 3, 5, 7, 8, 1];
        assert_eq!(average(&ints), 4.166666666666667);
        assert_eq!(median(&ints), 6.0);
        assert_eq!(mode(&ints), 1);
    }
}

fn main() {
    let ints = vec![1,3,5,7,8,1];
    println!("Average is {}", average(&ints));
    println!("Median is {}", median(&ints));
    println!("Mode is {}", mode(&ints));
    println!("{:?}", ints);
}

fn average(ints : &[i32]) -> f64 {
    assert!(!ints.is_empty(), "must not be empty");

    ints.iter().sum::<i32>() as f64 / ints.len() as f64
}

fn median(ints : &[i32]) -> f64 {
    assert!(!ints.is_empty(), "must not be empty");

    let mut ints = ints.to_owned();
    ints.sort();
    match ints.len() % 2 {
      0 => average(&vec![ints[(ints.len() / 2)], ints[(ints.len() / 2) + 1]]),
      1 => ints[(ints.len() / 2)] as f64,
      _ => unreachable!()
    }
}

fn mode(ints: &[i32]) -> i32 {
    assert!(!ints.is_empty(), "must not be empty");

    let max = ints
        .iter()
        .fold(HashMap::new(), |mut acc, i| {
            *acc.entry(i).or_insert(0) += 1;
            acc
        })
        .into_iter()
        .max_by_key(|&(_, count)| count);

    match max {
        Some((val, _)) => *val,
        _ => -1,
    }
}