Two Boys in a Canoe

type WeightType = u32;
const TARGET_WEIGHT: WeightType = 150;

#[derive(Clone, Debug)]
pub struct Boy {
    name: String,
    weight: WeightType,
}

pub type CubPack = Vec<Boy>;

#[derive(Debug)]
pub enum Canoe {
    Solo(Boy),
    Duet(Boy, Boy),
}

impl Canoe {
    fn weight(&self) -> WeightType {
        match *self {
            Canoe::Solo(ref boy) => boy.weight,
            Canoe::Duet(ref b0, ref b1) => b0.weight + b1.weight,
        }
    }
}

pub type Canoes = Vec<Canoe>;

pub fn assign_canoes(cubs: &CubPack) -> Canoes {
    let mut canoes: Canoes = Vec::new();
    let mut cubs = cubs.clone();
    cubs.sort_by_key(|boy| boy.weight + 0);
    let mut assigned: Vec<bool> = cubs.iter().map(|_| false).collect();
    let mut heavy = cubs.len();
    for light in 0..cubs.len() {
        if assigned[light] {
            continue;
        }
        while !assigned[light] && heavy > light + 1 {
            if cubs[light].weight + cubs[heavy - 1].weight <= TARGET_WEIGHT {
                assigned[light] = true;
                assigned[heavy - 1] = true;
                canoes.push(Canoe::Duet(cubs[light].clone(),
                                        cubs[heavy - 1].clone()));
            }
            heavy -= 1;
        }
        if !assigned[light] {
            canoes.push(Canoe::Solo(cubs[light].clone()));
            assigned[light] = true;
        }
    }
    canoes
}

fn cub_pack() -> CubPack {
    vec![
        Boy { name: "Billy".to_string(), weight: 93 },
        Boy { name: "Timmy".to_string(), weight: 67 },
        Boy { name: "Johnny".to_string(), weight: 119 },
        Boy { name: "Bobby".to_string(), weight: 113 },
        Boy { name: "Ralphie".to_string(), weight: 110 },
        Boy { name: "Bart".to_string(), weight: 114 },
        Boy { name: "Carter".to_string(), weight: 83 },
        Boy { name: "Davey".to_string(), weight: 101 },
        Boy { name: "Kevin".to_string(), weight: 47 },
        Boy { name: "Alan".to_string(), weight: 112 },
        Boy { name: "Eric".to_string(), weight: 49 },
        Boy { name: "Craig".to_string(), weight: 54 },
        Boy { name: "Brad".to_string(), weight: 85 },
    ]
}
fn main() {
    let canoes = assign_canoes(&cub_pack());
    for canoe in canoes {
        match canoe {
            Canoe::Solo(ref boy) => {
                println!("{} lb: {}", canoe.weight(), boy.name)
            }
            Canoe::Duet(ref b0, ref b1) => {
                println!("{} lb: {}, {}", canoe.weight(), b0.name, b1.name)
            }
        }
    }
}

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

    #[test]
    fn test_none() {
        let cub_pack: CubPack = vec![];
        let canoes = assign_canoes(&cub_pack);
        assert!(canoes.len() == 0);
    }

    #[test]
    fn test_solos() {
        let cub_pack: CubPack = vec![
            Boy { name: "Billy".to_string(), weight: 85 },
            Boy { name: "Timmy".to_string(), weight: 80 },
            ];
        let canoes = assign_canoes(&cub_pack);
        assert!(canoes.len() == 2);
        if let Canoe::Solo(ref boy) = canoes[0] {
            assert!(boy.name == "Timmy");
            assert!(boy.weight == 80);
        } else {
            panic!("");
        }
        if let Canoe::Solo(ref boy) = canoes[1] {
            assert!(boy.name == "Billy");
            assert!(boy.weight == 85);
        } else {
            panic!("");
        }
    }

    #[test]
    fn test_duet() {
        let cub_pack: CubPack = vec![
            Boy { name: "Billy".to_string(), weight: 80 },
            Boy { name: "Timmy".to_string(), weight: 70 },
            ];
        let canoes = assign_canoes(&cub_pack);
        assert!(canoes.len() == 1);
        if let Canoe::Duet(ref b0, ref b1) = canoes[0] {
            assert!(b0.name == "Timmy");
            assert!(b0.weight == 70);
            assert!(b1.name == "Billy");
            assert!(b1.weight == 80);
        } else {
            panic!("");
        }
    }

    #[test]
    fn test_mixed() {
        let cub_pack: CubPack = vec![
            Boy { name: "Billy".to_string(), weight: 80 },
            Boy { name: "Kevin".to_string(), weight: 70 },
            Boy { name: "Timmy".to_string(), weight: 70 },
            ];
        let canoes = assign_canoes(&cub_pack);
        assert!(canoes.len() == 2);
        if let Canoe::Duet(ref b0, ref b1) = canoes[0] {
            assert!(b0.name == "Kevin");
            assert!(b0.weight == 70);
            assert!(b1.name == "Billy");
            assert!(b1.weight == 80);
        } else {
            panic!("");
        }
        if let Canoe::Solo(ref boy) = canoes[1] {
            assert!(boy.name == "Timmy");
            assert!(boy.weight == 70);
        } else {
            panic!("");
        }
    }
}