collections

BTreeMap

  • clear(&mut self) Clears the map, removing all elements.
  • get(&self, key: &Q) Returns a reference to the value corresponding to the key.
  • get_key_value(&self, k: &Q)
  • first_key_value(&self) eturns the first key-value pair in the map.
  • first_entry(&mut self) Returns the first entry in the map for in-place manipulation
  • pop_first(&mut self)
  • last_key_value(&self)
  • last_entry(&mut self)
  • pop_last(&mut self)
  • contains_key(&self, key: &Q)
  • get_mut(&mut self, key: &Q) Returns a mutable reference to the value corresponding to the key
  • insert(&mut self, key: K, value: V)
  • try_insert(&mut self, key: K, value: V) If the map already had this key present, nothing is updated, and an error containing the occupied entry and the value is returned.
  • remove(&mut self, key: &Q)
  • remove_entry(&mut self, key: &Q)
  • retain<F>(&mut self, mut f: F) Retains only the elements specified by the predicate.
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    use std::collections::BTreeMap;
    let mut map: BTreeMap<i32, i32> = (0..8).map(|x| (x, x*10)).collect();
    // Keep only the elements with even-numbered keys.
    map.retain(|&k, _| k % 2 == 0);
    assert!(map.into_iter().eq(vec![(0, 0), (2, 20), (4, 40), (6, 60)]));
  • append(&mut self, other: &mut Self) Moves all elements from other into self, leaving other empty.
  • range<T: ?Sized, R>(&self, range: R) -> Range<'_, K, V> Constructs a double-ended iterator over a sub-range of elements in the map.
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    use std::collections::BTreeMap;
    use std::ops::Bound::Included;
    let mut map = BTreeMap::new();
    map.insert(3, "a");
    map.insert(5, "b");
    map.insert(8, "c");
    for (&key, &value) in map.range((Included(&4), Included(&8))) {
        println!("{key}: {value}");
    }
    assert_eq!(Some((&5, &"b")), map.range(4..).next());
  • range_mut<T: ?Sized, R>(&mut self, range: R) -> RangeMut<'_, K, V>
  • entry(&mut self, key: K) Gets the given key’s corresponding entry in the map for in-place manipulation.
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    use std::collections::BTreeMap;
    let mut count: BTreeMap<&str, usize> = BTreeMap::new();
    // count the number of occurrences of letters in the vec
    for x in ["a", "b", "a", "c", "a", "b"] {
        count.entry(x).and_modify(|curr| *curr += 1).or_insert(1);
    }
    assert_eq!(count["a"], 3);
    assert_eq!(count["b"], 2);
    assert_eq!(count["c"], 1);
  • split_off<Q: ?Sized + Ord>(&mut self, key: &Q) Splits the collection into two at the given key. Returns everything after the given key,
  • drain_filter<F>(&mut self, pred: F) Creates an iterator that visits all elements (key-value pairs) in ascending key order and uses a closure to determine if an element should be removed. If the closure returns true, the element is removed from the map and yielded. If the closure returns false, or panics, the element remains in the map and will not be yielded
  • into_keys(self) Creates a consuming iterator visiting all the keys, in sorted order. The map cannot be used after calling this
  • into_values(self)