all_lab_free_trees.hpp

/*********************************************************************
 *
 * Linear Arrangement Library - A library that implements a collection
 * algorithms for linear arrangments of graphs.
 *
 * Copyright (C) 2019 - 2024
 *
 * This file is part of Linear Arrangement Library. The full code is available
 * at:
 *      https://github.com/LAL-project/linear-arrangement-library.git
 *
 * Linear Arrangement Library is free software: you can redistribute it
 * and/or modify it under the terms of the GNU Affero General Public License
 * as published by the Free Software Foundation, either version 3 of the
 * License, or (at your option) any later version.
 *
 * Linear Arrangement Library 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 Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with Linear Arrangement Library.  If not, see <http://www.gnu.org/licenses/>.
 *
 * Contact:
 *
 *     Lluís Alemany Puig (lluis.alemany.puig@upc.edu)
 *         LQMC (Quantitative, Mathematical, and Computational Linguisitcs)
 *         CQL (Complexity and Quantitative Linguistics Lab)
 *         Jordi Girona St 1-3, Campus Nord UPC, 08034 Barcelona.   CATALONIA, SPAIN
 *         Webpage: https://cqllab.upc.edu/people/lalemany/
 *
 *     Ramon Ferrer i Cancho (rferrericancho@cs.upc.edu)
 *         LQMC (Quantitative, Mathematical, and Computational Linguisitcs)
 *         CQL (Complexity and Quantitative Linguistics Lab)
 *         Office 220, Omega building
 *         Jordi Girona St 1-3, Campus Nord UPC, 08034 Barcelona.   CATALONIA, SPAIN
 *         Webpage: https://cqllab.upc.edu/people/rferrericancho/
 *
 ********************************************************************/
 
#pragma once
 
// lal includes
#include <lal/basic_types.hpp>
#include <lal/graphs/free_tree.hpp>
#include <lal/generate/tree_generator.hpp>
#include <lal/detail/array.hpp>
 
namespace lal {
namespace generate {
 
class all_lab_free_trees : public _tree_generator<graphs::free_tree> {
public:
    /* CONSTRUCTORS */
 
    all_lab_free_trees() noexcept : _tree_generator<graphs::free_tree>() { }
 
    all_lab_free_trees(const uint64_t n) noexcept {
        init(n);
    }
 
    all_lab_free_trees(const all_lab_free_trees& Gen) noexcept = default;
 
    all_lab_free_trees(all_lab_free_trees&& Gen) noexcept = default;
 
    ~all_lab_free_trees() = default;
 
    all_lab_free_trees& operator= (const all_lab_free_trees& g) noexcept = default;
    all_lab_free_trees& operator= (all_lab_free_trees&& g) noexcept = default;
 
    /* INITIALIZE */
 
    void init(const uint64_t n) noexcept {
        _tree_generator::init(n);
        m_Prufer_seq.resize(m_n <= 2 ? 1 : m_n - 2, 0);
        m_sm.resize(m_n <= 2 ? 1 : m_n - 2, 0);
        reset();
    }
 
    void clear() noexcept {
        _tree_generator::clear();
        m_Prufer_seq.clear();
        m_sm.clear();
    }
 
    /* GETTERS */
 
    [[nodiscard]] bool end() const noexcept { return m_reached_end; }
 
    /* MODIFIERS */
 
    void next() noexcept {
        if (not has_next() or m_reached_end) {
            m_reached_end = true;
            return;
        }
 
        if (m_n <= 2) {
            // there is only one tree we can make
            m_sm[0] = 1;
            return;
        }
 
        while (m_it > 0 and m_Prufer_seq[m_it] == m_n - 1) {
            --m_it;
        }
        ++m_Prufer_seq[m_it];
 
        m_sm[m_it] =
        (m_Prufer_seq[m_it] == m_n - 1 ?
            (m_it == 0) or (m_sm[m_it - 1] and m_Prufer_seq[m_it - 1] == m_n - 1)
            :
            m_sm[m_it]
        );
 
        ++m_it;
        if (m_it < m_Prufer_seq.size()) {
            std::fill(m_Prufer_seq.begin() + m_it, m_Prufer_seq.end(), 0);
        }
        m_it = m_n - 3;
    }
 
    void reset() noexcept {
        activate_all_postprocessing_actions();
        __reset();
        next();
    }
 
    [[nodiscard]] graphs::free_tree yield_tree() noexcept {
        const auto t = get_tree();
        next();
        return t;
    }
 
protected:
    graphs::free_tree __get_tree() noexcept;
 
    void __reset() noexcept {
        m_reached_end = false;
 
        if (m_n <= 2) {
            m_sm[0] = 0;
            // there is only one tree we can make
            return;
        }
 
        m_it = 0;
        m_sm.fill(false);
        m_Prufer_seq.fill(0);
        // place 'it' at the end of the sequence
        m_it = m_n - 3;
        // make sure that the first call to next()
        // produces the sequence 0 0 ... 0
        m_Prufer_seq[m_it] = static_cast<uint64_t>(-1);
        m_L = m_n - 2;
    }
 
    [[nodiscard]] bool has_next() const noexcept {
        return m_sm[(m_n <= 2 ? 0 : m_n - 3)] == 0;
    }
 
private:
    uint64_t m_it;
    uint64_t m_L;
    detail::array<uint64_t> m_Prufer_seq;
    detail::array<char> m_sm;
    bool m_reached_end = false;
};
 
} // -- namespace generate
} // -- namespace lal