aoc/2022/1/src/main.rs

use std::cmp::Ordering;
use std::str::FromStr;

fn main() {

    let mut input_file = Some("input".to_string());
    let mut args = std::env::args();
    while args.len() > 0 {
        let arg = args.nth(0);
        if arg.unwrap().eq("-f") {
            let value = args.nth(0);
            if value.is_some() {
                input_file = value;
            }
            else {
                println!("No value after argument: '-f'");
            }
        }
    }
    println!("Input file: '{:?}'", input_file);
    let mut elves = elves_from_file(&input_file.unwrap()).expect("failed to read file");
    elves.sort_by(|a, b| b.cmp_by_calories(a));
    println!("[PART 1] Elf with most calories: {}", elves[0].calories());

    let p2_elves: std::vec::Vec::<_> = elves.into_iter()
        .enumerate()
        .filter(|&(i, _)| i < 3 )
        .map(|(_, e)| e)
        .collect();
    let mut p2_calories: u32 = 0;
    for x in p2_elves {
        p2_calories += x.calories();
    }
    println!("[PART 2] Top 3 elves have these calories: {}", p2_calories);
}

struct Elf {
    items: std::vec::Vec<u32>,
}

impl Elf {
    fn calories(&self) -> u32 {
        let mut value = 0;
        for x in &self.items {
            value += x;
        }
        return value;
    }

    fn cmp_by_calories(&self, b: &Elf) -> Ordering {
        return self.calories().cmp(&b.calories());
    }
}

fn elves_from_file(file_name: &String) -> std::result::Result<std::vec::Vec::<Elf>, String> {
    let contents = std::fs::read_to_string(file_name).expect("Couldn't read contents of file");
    return std::result::Result::Ok(elves_from_string(&contents));
}

fn elves_from_string(contents: &String) -> std::vec::Vec::<Elf> {
    let mut elves = std::vec::Vec::<Elf>::new();
    let mut current_elf = Elf {
        items: std::vec::Vec::<u32>::new(),
    };
    for line in contents.lines() {
        if line.eq("") {
            elves.push(current_elf);
            current_elf = Elf {
                items: std::vec::Vec::<u32>::new(),
            };
        }
        else {
            match u32::from_str(&line) {
                Ok(v) => {
                    current_elf.items.push(v);
                },
                Err(_) => {
                    println!("WARNING: '{}' does not convert to u32, skipping.", line);
                    continue;
                },
            }
        }
    }
    if current_elf.items.len() > 0 {
        elves.push(current_elf);
    }
    return elves;
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_from_empty_string() {
        let contents = "".to_string();
        let elves = elves_from_string(&contents);
        assert_eq!(elves.len(), 0);
    }

    #[test]
    fn test_from_string() {
        let contents = r#"1000
2000
3000

4000

5000
6000

7000
8000
9000

10000
"#.to_string();
        let elves = elves_from_string(&contents);
        assert_eq!(elves.len(), 5);
        let first = vec![1000, 2000, 3000];
        assert!(first.eq(&elves[0].items));
        let last = vec![10000];
        assert!(last.eq(&elves[4].items));
    }

    #[test]
    fn test_calories() {
        let mut elf = Elf {
            items: std::vec::Vec::<u32>::new(),
        };
        assert_eq!(elf.calories(), 0);

        elf.items.push(1000);
        elf.items.push(10000);

        assert_eq!(elf.calories(), 11000);
    }

    #[test]
    fn test_sort() {
        let mut v = std::vec::Vec::<Elf>::new();
        v.push(Elf {
            items: vec![5000, 50000],
        });
        v.push(Elf {
            items: vec![1000, 10000],
        });
        assert_eq!(v[0].calories(), 55000);
        v.sort_by(|a, b| a.cmp_by_calories(b));
        assert_eq!(v[0].calories(), 11000);
    }
}