1#![cfg(feature = "use_std")]
2
3use std::collections::HashMap;
4use std::hash::Hash;
5use std::iter::Iterator;
6
7/// Return a `HashMap` of keys mapped to a list of their corresponding values.
8///
9/// See [`.into_group_map()`](crate::Itertools::into_group_map)
10/// for more information.
11pub fn into_group_map<I, K, V>(iter: I) -> HashMap<K, Vec<V>>
12where
13 I: Iterator<Item = (K, V)>,
14 K: Hash + Eq,
15{
16 let mut lookup: HashMap> = HashMap::new();
17
18 iter.for_each(|(key: K, val: V)| {
19 lookup.entry(key).or_insert_with(default:Vec::new).push(val);
20 });
21
22 lookup
23}
24
25pub fn into_group_map_by<I, K, V>(iter: I, f: impl Fn(&V) -> K) -> HashMap<K, Vec<V>>
26where
27 I: Iterator<Item = V>,
28 K: Hash + Eq,
29{
30 into_group_map(iter.map(|v: V| (f(&v), v)))
31}
32