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/*
* Copyright 2007-2009 Ben Boeckel <MathStuf@gmail.com>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/**
* \file sigcore/Hat.h
*/
#ifndef SIGCORE_HAT
#define SIGCORE_HAT
// Sigcore includes
#include "Fraction.h"
#include "Global.h"
// Qt includes
#include <QtCore/QtGlobal>
#include <QtCore/QMap>
// Standard includes
#include <cstdlib>
namespace Sigcore
{
/**
* \class Sigcore::Hat Hat.h sigcore/Hat.h
* \brief Class to help choose items from a weighted set of items.
*
* Given a set of weighted items to choose from, Hat will pick out a random item from the set.
*/
template<class T> class SIGCORE_EXPORT Hat
{
public:
/**
* Default constructor.
*/
Hat();
/**
* Choose an item from the set without removal.
*
* \return The item chosen.
*/
T pick() const;
/**
* Choose an item from the set with removal.
*
* \return The item chosen.
*/
T take();
/**
* Choose an item from the set as well as all identical items.
*
* \return The item chosen.
*/
T takeAndClear();
/**
* Set the weight of an item in the set.
*
* \param key The item to set.
* \param weight The weight of the item.
*/
void setCount(const T& key, const int weight);
/**
* Add a number of items to the set.
*
* \param key The item to add to the set.
* \param weight How many of the item to add.
*/
void add(const T& key, const int weight);
/**
* \return The number of distinct items in the set.
*/
int distinctCount() const;
/**
* \return The number of total items in the set.
*/
int count() const;
/**
* \param key The item to get the count of.
*
* \return The amount of \p key in the set.
*/
int count(const T& key) const;
/**
* \param key The item to get the chance of.
*
* \return The chance of choosing \p key.
*/
Fraction chance(const T& key) const;
private:
QMap<T, int> m_items;
int m_count;
};
template<class T> inline Hat<T>::Hat() :
m_count(0)
{
}
template<class T> inline T Hat<T>::pick() const
{
if (!m_count)
return T();
int choice = drand48() * m_count;
QList<T> keys = m_items.keys();
foreach (const T& key, keys)
{
choice -= m_items[key];
if (choice < 0)
return key;
}
return T();
}
template<class T> inline T Hat<T>::take()
{
if (!m_count)
return T();
T chosen = pick();
if (!(--m_items[chosen]))
m_items.remove(chosen);
--m_count;
return chosen;
}
template<class T> inline T Hat<T>::takeAndClear()
{
T chosen = pick();
m_count -= m_items[chosen];
m_items.remove(chosen);
return chosen;
}
template<class T> inline void Hat<T>::setCount(const T& key, const int weight)
{
add(key, weight - m_items[key]);
}
template<class T> inline void Hat<T>::add(const T& key, const int weight)
{
int nWeight = qMax(weight, -m_items[key]);
m_items[key] += nWeight;
m_count += nWeight;
if (!m_items[key])
m_items.remove(key);
}
template<class T> inline int Hat<T>::distinctCount() const
{
return m_items.size();
}
template<class T> inline int Hat<T>::count() const
{
return m_count;
}
template<class T> inline int Hat<T>::count(const T& key) const
{
if (m_items.contains(key))
return m_items[key];
return 0;
}
template<class T> inline Fraction Hat<T>::chance(const T& key) const
{
return Fraction(count(key), m_count);
}
}
#endif
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