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use std::collections::HashMap;
use std::hash::Hash;
pub trait IteratorExt<Item>
{
fn find_duplicate(&mut self) -> Option<Item>;
}
impl<Iter> IteratorExt<Iter::Item> for Iter
where
Iter: Iterator,
Iter::Item: Eq + Hash + Clone,
{
fn find_duplicate(&mut self) -> Option<Iter::Item>
{
let mut iterated_item_map = HashMap::<Iter::Item, ()>::new();
for item in self {
if iterated_item_map.contains_key(&item) {
return Some(item);
}
iterated_item_map.insert(item, ());
}
None
}
}
#[cfg(test)]
mod tests
{
use super::*;
#[test]
fn can_find_duplicate()
{
#[derive(Debug, PartialEq, Eq, Clone, Hash)]
struct Fruit
{
name: String,
}
assert_eq!(
vec![
Fruit {
name: "Apple".to_string(),
},
Fruit {
name: "Banana".to_string(),
},
Fruit {
name: "Apple".to_string(),
},
Fruit {
name: "Orange".to_string(),
},
]
.iter()
.find_duplicate(),
Some(&Fruit {
name: "Apple".to_string()
})
);
assert_eq!(
vec![
Fruit {
name: "Banana".to_string(),
},
Fruit {
name: "Apple".to_string(),
},
Fruit {
name: "Orange".to_string(),
},
]
.iter()
.find_duplicate(),
None
);
}
}
|
