# Mnemonist

## SparseSet

A `SparseSet` is a very time-efficient set structure used to store a range of unsigned integers. Note however that this structure can consume a lot of memory (it relies on two byte arrays having a length equal to the maximum integer you need to store).

Contrary to the `BitSet`, the `SparseSet` is very efficient if you need to iterate over the stored value or if you often need to clear the set.

If you also need to associate values to the set’s members, take a look to `SparseMap` instead.

``````const SparseSet = require('mnemonist/sparse-set');
``````

## Constructor

``````const set = new SparseSet(length);
``````

## Methods

Mutation

Iteration

### #.length

Length of the set, that is to say the maximum number one can expect to store in this set minus one.

``````const set = new SparseSet(4);

set.length;
>>> 4
``````

### #.size

Number of items currently in the set.

``````const set = new SparseSet(4);

set.size;
>>> 0

set.size;
>>> 1
``````

Adds a number to the set.

`O(1)`

``````const set = new SparseSet(4);

set.has(2);
>>> true
``````

### #.delete

Deletes the given number from the set.

`O(1)`

``````const set = new SparseSet(4);

set.delete(2);
set.has(2);
>>> false
``````

Resets every number stored by the set.

``````const set = new SparseSet(4);

set.set(1);
set.set(3);

set.clear();
set.size
>>> 0
``````

### #.has

Returns whether the given number exists in the set.

`O(1)`

``````const set = new SparseSet(4);

set.has(3);
>>> false

set.has(3);
>>> true
``````

### #.forEach

Iterates over the set’s numbers.

``````const set = new SparseSet(4);

set.forEach((number) => {
console.log(number);
});
``````

### #.values

Returns an iterator over the set’s number.

``````const set = new SparseSet(4);

const iterator = set.values()

iteraror.next().value
>>> 2
``````

### Iterable

Alternatively, you can iterate over a set’s values using ES2015 `for...of` protocol:

``````const set = new SparseSet(4);

for (const number of set) {
console.log(number);
}
``````