Binary Heap

It heapify each element when changing values, so there are better ways to do it.

```

insert(key: string, value: number) {
        if (this.nodes.has(key)) {
            return;
        }
        const node = new Node(key, value);
        this.heap.insert(node);
        this.nodes.set(key, node);
        this.heap.heapifyAll(); // TODO
    }

changeKey(key: string, value: number) {
        if (!this.nodes.has(key)) {
            return;
        }
        let node = this.nodes.get(key);
        node = new Node(node.key, value, node.position);
        this.nodes.set(key, node);
        this.heap.set(node.position, node);
        this.heap.heapifyAll();  // TODO
}