18.7 Selecting the Appropriate Collection

When deciding which collection to use, consider:

  • Random integer indexing needed?
    Use a Vec<T>.
  • Dynamically growable text?
    Use String.
  • Fast lookups with arbitrary keys?
    Use a HashMap<K, V>.
  • Key-value pairs in sorted order?
    Use BTreeMap<K, V>.
  • Need a set of unique items?
    Use HashSet<T> or BTreeSet<T>.
  • Frequent push/pop at both ends?
    Use VecDeque<T>.
  • Frequent insertion/removal in the middle at known locations?
    Use LinkedList<T>, but confirm it’s really necessary (a Vec<T> can still be surprisingly efficient).