sparse set is a data-structure with fast iteration and getting data from sparse ID
Sparse set has 2 arrays,the sparse array 'S' and dense array 'D'. The 'S' and 'D' array must satisfy 2 rules :
S[ID] == indexD[index] = ID
These 2 rules make us get data from ID quickly and we can store all data densely.
Because we need store data and entity ID. XSparseSet has 3 arrays , "indices" "entities" and "data".
- indices : the sparse array
- entities : the dense array
- data : the dense array
let mut sparse_set = SparseSet::new();
sparse_set.add(4,'c');
sparse_set.add(7,'a');
assert_eq!(sparse_set.get(4),Some(&'c'));
assert_eq!(sparse_set.get(5),None);