1 #![cfg(feature = "use_std")]
2
3 use std::collections::HashMap;
4 use std::hash::Hash;
5 use 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.
into_group_map<I, K, V>(iter: I) -> HashMap<K, Vec<V>> where I: Iterator<Item=(K, V)>, K: Hash + Eq,11 pub fn into_group_map<I, K, V>(iter: I) -> HashMap<K, Vec<V>>
12 where I: Iterator<Item=(K, V)>,
13 K: Hash + Eq,
14 {
15 let mut lookup = HashMap::new();
16
17 iter.for_each(|(key, val)| {
18 lookup.entry(key).or_insert_with(Vec::new).push(val);
19 });
20
21 lookup
22 }
23
into_group_map_by<I, K, V>(iter: I, f: impl Fn(&V) -> K) -> HashMap<K, Vec<V>> where I: Iterator<Item=V>, K: Hash + Eq,24 pub fn into_group_map_by<I, K, V>(iter: I, f: impl Fn(&V) -> K) -> HashMap<K, Vec<V>>
25 where
26 I: Iterator<Item=V>,
27 K: Hash + Eq,
28 {
29 into_group_map(
30 iter.map(|v| (f(&v), v))
31 )
32 }
33