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/*
* partition.h -- a disjoint set of pairwise equivalent items
*
* Copyright (c) 2007-2010, Dmitry Prokoptsev <dprokoptsev@gmail.com>,
* Alexander Gololobov <agololobov@gmail.com>
*
* This file is part of Pire, the Perl Incompatible
* Regular Expressions library.
*
* Pire is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Pire is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Lesser Public License for more details.
* You should have received a copy of the GNU Lesser Public License
* along with Pire. If not, see <http://www.gnu.org/licenses>.
*/
#ifndef PIRE_PARTITION_H
#define PIRE_PARTITION_H
#include <contrib/libs/pire/pire/stub/stl.h>
#include <contrib/libs/pire/pire/stub/singleton.h>
namespace Pire {
/*
* A class which forms a disjoint set of pairwise equivalent items,
* depending on given equivalence relation.
*/
template<class T, class Eq>
class Partition {
private:
typedef TMap< T, ypair< size_t, TVector<T> > > Set;
public:
Partition(const Eq& eq)
: m_eq(eq)
, m_maxidx(0)
{
}
/// Appends a new item into partition, creating new equivalience class if neccessary.
void Append(const T& t) {
DoAppend(m_set, t);
}
typedef typename Set::const_iterator ConstIterator;
ConstIterator Begin() const {
return m_set.begin();
}
ConstIterator begin() const {
return m_set.begin();
}
ConstIterator End() const {
return m_set.end();
}
ConstIterator end() const {
return m_set.end();
}
size_t Size() const {
return m_set.size();
}
bool Empty() const {
return m_set.empty();
}
/// Returns an item equal to @p t. It is guaranteed that:
/// - representative(a) equals representative(b) iff a is equivalent to b;
/// - representative(a) is equivalent to a.
const T& Representative(const T& t) const
{
auto it = m_inv.find(t);
if (it != m_inv.end())
return it->second;
else
return DefaultValue<T>();
}
bool Contains(const T& t) const
{
return m_inv.find(t) != m_inv.end();
}
/// Returns an index of set containing @p t. It is guaranteed that:
/// - index(a) equals index(b) iff a is equivalent to b;
/// - 0 <= index(a) < size().
size_t Index(const T& t) const
{
auto it = m_inv.find(t);
if (it == m_inv.end())
throw Error("Partition::index(): attempted to obtain an index of nonexistent item");
auto it2 = m_set.find(it->second);
Y_ASSERT(it2 != m_set.end());
return it2->second.first;
}
/// Returns the whole equivalence class of @p t (i.e. item @p i
/// is returned iff representative(i) == representative(t)).
const TVector<T>& Klass(const T& t) const
{
auto it = m_inv.find(t);
if (it == m_inv.end())
throw Error("Partition::index(): attempted to obtain an index of nonexistent item");
auto it2 = m_set.find(it->second);
Y_ASSERT(it2 != m_set.end());
return it2->second.second;
}
bool operator == (const Partition& rhs) const { return m_set == rhs.m_set; }
bool operator != (const Partition& rhs) const { return !(*this == rhs); }
/// Splits the current sets into smaller ones, using given equivalence relation.
/// Requires given relation imply previous one (set either in ctor or
/// in preceeding calls to split()), but performs faster.
/// Replaces previous relation with given one.
void Split(const Eq& eq)
{
m_eq = eq;
for (auto&& element : m_set)
if (element.second.second.size() > 1) {
TVector<T>& v = element.second.second;
auto bound = std::partition(v.begin(), v.end(), std::bind2nd(m_eq, v[0]));
if (bound == v.end())
continue;
Set delta;
for (auto it = bound, ie = v.end(); it != ie; ++it)
DoAppend(delta, *it);
v.erase(bound, v.end());
m_set.insert(delta.begin(), delta.end());
}
}
private:
Eq m_eq;
Set m_set;
TMap<T, T> m_inv;
size_t m_maxidx;
void DoAppend(Set& set, const T& t)
{
auto it = set.begin();
auto end = set.end();
for (; it != end; ++it)
if (m_eq(it->first, t)) {
it->second.second.push_back(t);
m_inv[t] = it->first;
break;
}
if (it == end) {
// Begin new set
TVector<T> v(1, t);
set.insert(ymake_pair(t, ymake_pair(m_maxidx++, v)));
m_inv[t] = t;
}
}
};
// Mainly for debugging
template<class T, class Eq>
yostream& operator << (yostream& stream, const Partition<T, Eq>& partition)
{
stream << "Partition {\n";
for (auto&& partitionElement : partition) {
stream << " Class " << partitionElement.second.first << " \"" << partitionElement.first << "\" { ";
bool first = false;
for (auto&& element : partitionElement.second.second) {
if (first)
stream << ", ";
else
first = true;
stream << element;
}
stream << " }\n";
}
stream << "}";
return stream;
}
}
#endif
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