seperated singletons

wordcount.rs

use std::io::{self, Read, Write, BufWriter};
use std::collections::HashMap;

fn main() {
    let mut buffer = String::new();
    io::stdin().read_to_string(&mut buffer).ok();

    let mut words: HashMap<&str, usize> = HashMap::new();
    for word in buffer.split(is_whitespace).filter(is_not_empty) {
        if let Some(count) = words.get_mut(word) {
            *count += 1;
            continue;
        }
        words.insert(word, 1);
    }

    let mut multiple: Vec<(&str, usize)> = vec![];
    let mut single: Vec<(&str, usize)> = vec![];

    // we create split all words into two vectors,
    // one with multiple occurences and one Vector 
    // with single occurences
    for (word, count) in words.iter() {
        if *count > 1 {
            multiple.push((*word, *count));
        } else {
            single.push((*word, *count));
        }
    }

    multiple.sort_by_key(|a| a.0);
    multiple.sort_by(|a, b| b.1.cmp(&a.1));
    single.sort_by_key(|a| a.0);

    let mut output = BufWriter::new(io::stdout());
    for word in multiple {
        writeln!(output, "{}\t{}", word.0, word.1).ok();
    }

    for word in single {
        writeln!(output, "{}\t{}", word.0, word.1).ok();
    }
}

#[inline]
fn is_not_empty(s: &&str) -> bool {
    !s.is_empty()
}

#[inline]
fn is_whitespace(c: char) -> bool {
    c == ' ' || c == '\t' || c == '\n'
}