ARMANRIAZIRSTCollectionHasMapavoid_of_duplicate
Default setting which is using insert you will have any duplicated key or val.
map.insert(key, "some value".into());
but when we use entry(word).or_insert(0) that will make avoid duplicated k/v.
let mut map = HashMap::<CompoundKey, String>::new();
let tmp = map.entry(word).or_insert(0);
ArmanRiazi