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CGAL::Union_find<T,A>

Definition

An instance P of the data type Union_find<T,A> is a partition of values of type T into disjoint sets. The template parameter A has to be a model of the allocator concept as defined in the C++ standard. It has a default argument CGAL_ALLOCATOR(T).

#include <CGAL/Union_find.h>

Types

Union_find<T,A>::value_type
values stored in items (equal to T).


Union_find<T,A>::handle
handle to values.


Union_find<T,A>::iterator
iterator over values.

There are also constant versions const_handle and const_iterator.

Union_find<T,A>::allocator
allocator.

Creation

Union_find<T,A> P;
creates an instance P of type Union_find<T,A> and initializes it to the empty partition.

Operations

allocator P.get_allocator () the allocator of P.

std::size_t P.number_of_sets () returns the number of disjoint sets of P.

std::size_t P.size () returns the number of values of P.

std::size_t P.bytes () returns the memory consumed by P.

std::size_t P.size ( const_handle p) returns the size of the set containing p.

void P.clear () reinitializes P to an empty partition.

handle P.make_set ( T x) creates a new singleton set containing x and returns a handle to it.

handle P.push_back ( T x) same as make_set(x).

template <class Forward_iterator>
void P.insert ( Forward_iterator first, Forward_iterator beyond)
insert the range of values referenced by [first,beyond).
Requirement: value type of Forward_iterator is T.

handle P.find ( handle p)
const_handle P.find ( const_handle p) returns a canonical handle of the set that contains p, i.e., P.same_set(p,q) iff P.find(p) and P.find(q) return the same handle.
Precondition: p is a handle in P.

void P.unify_sets ( handle p, handle q)
unites the sets of partition P containing p and q.
Precondition: p and q are in P.

bool P.same_set ( const_handle p, const_handle q)
returns true iff p and q belong to the same set of P.
Precondition: p and q are in P.

iterator P.begin () returns an iterator pointing to the first value of P.

iterator P.end () returns an iterator pointing beyond the last value of P.

Implementation

Union_find<T,A> is implemented with union by rank and path compression. The running time for m set operations on n elements is O(n (m,n)) where (m,n) is the extremely slow growing inverse of Ackermann's function.

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CGAL Open Source Project. Release 3.4. 22 January 2009.