com.mxgraph.analysis
Class mxUnionFind

java.lang.Object
  com.mxgraph.analysis.mxUnionFind

public class mxUnionFind
extends Object

Implements a union find structure that uses union by rank and path compression. The union by rank guarantees worst case find time of O(log N), while Tarjan shows that in combination with path compression (halving) the average time for an arbitrary sequence of m >= n operations is O(m*alpha(m,n)), where alpha is the inverse of the Ackermann function, defined as follows: alpha(m,n) = min{i >= 1 | A(i, floor(m/n)) > log n} for m >= n >= 1 Which yields almost constant time for each individual operation.

Nested Class Summary

class

mxUnionFind.Node A class that defines the identity of a set.

Field Summary

protected Map<Object,mxUnionFind.Node>

nodes Maps from elements to nodes

Constructor Summary

mxUnionFind(Object[] elements)
Constructs a union find structure and initializes it with the specified elements.

Method Summary

boolean	differ(Object a, Object b) Returns true if element a and element b are not in the same set.
mxUnionFind.Node	find(mxUnionFind.Node node) Returns the set that contains node.
mxUnionFind.Node	getNode(Object element) Returns the node that represents element.
void	union(mxUnionFind.Node a, mxUnionFind.Node b) Unifies the sets a and b in constant time using a union by rank on the tree size.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

nodes

protected Map<Object,mxUnionFind.Node> nodes

Maps from elements to nodes

Constructor Detail

mxUnionFind

public mxUnionFind(Object[] elements)

Constructs a union find structure and initializes it with the specified elements.

Parameters:

elements -

Method Detail

getNode

public mxUnionFind.Node getNode(Object element)

Returns the node that represents element.

find

public mxUnionFind.Node find(mxUnionFind.Node node)

Returns the set that contains node. This implementation provides path compression by halving.

union

public void union(mxUnionFind.Node a,
                  mxUnionFind.Node b)

Unifies the sets a and b in constant time using a union by rank on the tree size.

differ

public boolean differ(Object a,
                      Object b)

Returns true if element a and element b are not in the same set. This uses getNode and then find to determine the elements set.

Parameters:

a - The first element to compare.

b - The second element to compare.

Returns:

Returns true if a and b are in the same set.

See Also:

getNode(Object)