rust book exercise

main.rs

use std::collections::HashMap;

fn mean(arr: &Vec<usize>) -> usize {
    let sum = arr.iter().fold(0, |sum, el| sum + el);
    sum / arr.len()
}

fn median(arr: &Vec<usize>) -> usize {
    let half_position = arr.len() / 2;
    let mut input_sorted = arr.clone();
    input_sorted.sort(); // this mutates the vec
    input_sorted[half_position]
}

fn mode(arr: &Vec<usize>) -> usize {
    let mut freq_map = HashMap::new();
    for &num in arr {
        *freq_map.entry(num).or_insert(0) += 1;
    }
    let mut sorted_freq: Vec<(&usize, &usize)> = freq_map.iter().collect();
    sorted_freq.sort_by(|(_, a), (_, &b)| b.cmp(a));
    *sorted_freq[0].0
}

fn main() {
    let input_numbers = vec![15, 20, 110, 5, 0, 2055, 11, 11, 11, 11 ,12, 2, 2, 23, 32, 23, 23, 2];

    println!("mean: {}", mean(&input_numbers));

    println!("median: {}", median(&input_numbers));

    println!("mode: {}", mode(&input_numbers));
}