| use std::collections::HashMap; | |
| use std::hash::Hash; | |
| /// Trait for grouping a collection of items by a key extracted from each item. | |
| pub trait GroupByKey<K, V> { | |
| fn group_by_key(value: Vec<V>, key_fn: impl Fn(&V) -> K) -> HashMap<K, Vec<V>>; | |
| } | |
| impl<K: Hash + Eq + Clone, V: Ord + Clone> GroupByKey<K, V> for Vec<V> { | |
| fn group_by_key(values: Vec<V>, key_fn: impl Fn(&V) -> K) -> HashMap<K, Vec<V>> { | |
| values | |
| .iter() | |
| .fold( | |
| HashMap::<K, Vec<&V>>::new(), | |
| |mut acc: HashMap<_, _>, chunk| { | |
| acc.entry(key_fn(chunk)).or_default().push(chunk); | |
| acc | |
| }, | |
| ) | |
| .into_iter() | |
| .map(|(key, mut chunks)| { | |
| chunks.sort(); | |
| (key.clone(), chunks.into_iter().cloned().collect::<Vec<_>>()) | |
| }) | |
| .collect::<HashMap<_, Vec<_>>>() | |
| } | |
| } | |