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lffg/grouping.rs

Last active July 13, 2023 16:44
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grouping.rs
use std::collections::BTreeMap;
fn group<'a>(data: impl Iterator<Item = (&'a str, u32)>) -> BTreeMap<&'a str, u32> {
data.fold(BTreeMap::new(), |mut map, (date, amount)| {
*map.entry(date).or_default() += amount;
map
})
}
#[test]
fn test() {
static DATA: &[(&str, u32)] = &[
("2023-07-13", 12),
("2023-07-14", 30),
("2023-07-13", 4),
("2023-07-14", 98),
("2023-07-12", 4),
("2023-07-12", 8),
("2023-07-12", 31),
("2023-07-15", 74),
("2023-07-13", 12),
("2023-07-12", 1),
("2023-07-17", 3),
("2023-07-16", 35),
];
assert_eq!(
group(DATA.iter().copied()),
BTreeMap::from([
("2023-07-12", 44),
("2023-07-13", 28),
("2023-07-14", 128),
("2023-07-15", 74),
("2023-07-16", 35),
("2023-07-17", 3),
])
);
}
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