Add ForestDisjointSet

bzip2
Graham 5 years ago
parent 0007da4729
commit e42fcd01b5
  1. 13
      util/src/main/java/dev/openrs2/util/collect/DisjointSet.java
  2. 165
      util/src/main/java/dev/openrs2/util/collect/ForestDisjointSet.java

@ -0,0 +1,13 @@
package dev.openrs2.util.collect;
public interface DisjointSet<T> extends Iterable<DisjointSet.Partition<T>> {
interface Partition<T> extends Iterable<T> {
/* empty */
}
Partition<T> add(T x);
Partition<T> get(T x);
void union(Partition<T> x, Partition<T> y);
int elements();
int partitions();
}

@ -0,0 +1,165 @@
package dev.openrs2.util.collect;
import java.util.ArrayDeque;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Queue;
public final class ForestDisjointSet<T> implements DisjointSet<T> {
private static final class Node<T> implements Partition<T> {
private final List<Node<T>> children = new ArrayList<>();
private final T value;
private Node<T> parent = this;
private int rank = 0;
private Node(T value) {
this.value = value;
}
private void setParent(Node<T> parent) {
this.parent = parent;
this.parent.children.add(this);
}
private Node<T> find() {
if (parent != this) {
parent = parent.find();
}
return parent;
}
@Override
public Iterator<T> iterator() {
return new NodeIterator<>(find());
}
@SuppressWarnings("unchecked")
@Override
public boolean equals(Object other) {
if (other == null || getClass() != other.getClass()) {
return false;
}
var node = (Node<T>) other;
return find() == node.find();
}
@Override
public int hashCode() {
return find().value.hashCode();
}
}
private static class NodeIterator<T> implements Iterator<T> {
private final Queue<Node<T>> queue = new ArrayDeque<>();
public NodeIterator(Node<T> root) {
this.queue.add(root);
}
@Override
public boolean hasNext() {
return !queue.isEmpty();
}
@Override
public T next() {
var node = queue.poll();
if (node == null) {
throw new NoSuchElementException();
}
queue.addAll(node.children);
return node.value;
}
}
private static class SetIterator<T> implements Iterator<Partition<T>> {
private final Iterator<Node<T>> it;
public SetIterator(ForestDisjointSet<T> set) {
this.it = new HashSet<>(set.nodes.values()).iterator();
}
@Override
public boolean hasNext() {
return it.hasNext();
}
@Override
public Partition<T> next() {
return it.next();
}
}
private final Map<T, Node<T>> nodes = new HashMap<>();
private int elements = 0, partitions = 0;
@Override
public Partition<T> add(T x) {
var node = nodes.get(x);
if (node != null) {
return node.find();
}
elements++;
partitions++;
nodes.put(x, node = new Node<>(x));
return node;
}
@Override
public Partition<T> get(T x) {
return get0(x);
}
private Node<T> get0(T x) {
var node = nodes.get(x);
if (node == null) {
return null;
}
return node.find();
}
@Override
public void union(Partition<T> x, Partition<T> y) {
var xRoot = ((Node<T>) x).find();
var yRoot = ((Node<T>) y).find();
if (xRoot == yRoot) {
return;
}
if (xRoot.rank < yRoot.rank) {
xRoot.setParent(yRoot);
} else if (xRoot.rank > yRoot.rank) {
yRoot.setParent(xRoot);
} else {
yRoot.setParent(xRoot);
xRoot.rank++;
}
partitions--;
}
@Override
public int elements() {
return elements;
}
@Override
public int partitions() {
return partitions;
}
@Override
public Iterator<Partition<T>> iterator() {
return new SetIterator<>(this);
}
}
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