minmax.hh 5.45 KB
Newer Older
1 2
// graph-tool -- a general graph modification and manipulation thingy
//
Tiago Peixoto's avatar
Tiago Peixoto committed
3
// Copyright (C) 2007-2012 Tiago de Paula Peixoto <tiago@skewed.de>
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214
//
// 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/>.

#ifndef MINMAX_HH
#define MINMAX_HH

#include <vector>
#include <boost/mpl/bool.hpp>
#include <iostream>
using namespace  std;

template <class Value, class Compare = std::less<Value> >
class double_priority_queue
{
public:
    double_priority_queue() {}
    double_priority_queue(const Compare& cmp): _cmp(cmp) {}

    size_t size() { return _queue.size(); }
    bool empty() { return _queue.empty(); }

    void push(const Value& v)
    {
        _queue.push_back(v);
        bubble_up(_queue.size()-1);
    }

    void pop_top()
    {
        // for (size_t i = 0; i < _queue.size(); ++i)
        //     if (_cmp(top(), _queue[i]))
        //     {
        //         cout << size_t(log2(i+1)) << endl;
        //         cout << "ops top" << endl;
        //         abort();
        //     }
        size_t i = &top() - &_queue[0];
        swap(_queue[i], _queue.back());
        _queue.pop_back();
        if (!_queue.empty())
            trickle_down(i);
    }

    void pop_bottom()
    {
        swap(_queue.front(), _queue.back());
        _queue.pop_back();
        if (!_queue.empty())
            trickle_down(0);
    }

    const Value& top()
    {
        if (_queue.size() < 2)
            return _queue[0];
        if (_queue.size() < 3)
            return _queue[1];
        if (_cmp(_queue[1], _queue[2]))
            return _queue[2];
        else
            return _queue[1];
    }

    const Value& bottom()
    {
        // for (size_t i = 0; i < _queue.size(); ++i)
        //     if (_cmp(_queue[i], _queue.front()))
        //         cout << "ops bottom" << endl;
        return _queue.front();
    }

    // general comparison: if IsMin is mpl::true_, then a < b, otherwise a > b
    // is computed
    template <class IsMin>
    bool cmp(size_t a, size_t b, IsMin)
    {
        if (IsMin::value)
            return _cmp(_queue[a], _queue[b]);
        else
            return _cmp(_queue[b], _queue[a]);
    }

    void trickle_down(size_t i)
    {
        if ((size_t(log2(i+1)) % 2) == 0)
            trickle_down(i, boost::mpl::true_());
        else
            trickle_down(i, boost::mpl::false_());
    }


    template <class IsMin>
    void trickle_down(size_t pos, IsMin is_min)
    {
        size_t i = pos;
        while (true)
        {
            size_t m = 2*i+1;
            if (m >= _queue.size())
                break;

            for (size_t j = 2*i+1; j < 2*i+3; ++j)
            {
                if (j >= _queue.size())
                    break;
                if (cmp(j, m, is_min))
                    m = j;
                for (size_t l = 2*j+1; l < 2*j+3; ++l)
                {
                    if (l >= _queue.size())
                        break;
                    if (cmp(l, m, is_min))
                        m = l;
                }
            }

            if (m > 2*i+2) // is grandchild
            {
                if (cmp(m, i, is_min))
                {
                    swap(_queue[m], _queue[i]);
                    if (!cmp(m, (m-1)/2, is_min))
                        swap(_queue[m], _queue[(m-1)/2]);
                    i = m;
                }
                else
                {
                    break;
                }
            }
            else
            {
                if (cmp(m, i, is_min))
                    swap(_queue[m], _queue[i]);
                break;
            }
        }
    }

    void bubble_up(size_t i)
    {
        if ((size_t(log2(i+1)) % 2) == 0)
        {
            if ((i > 0) && cmp(i, (i-1)/2, boost::mpl::false_()))
            {
                swap(_queue[i], _queue[(i-1)/2]);
                bubble_up((i-1)/2,  boost::mpl::false_());
            }
            else
            {
                bubble_up(i,  boost::mpl::true_());
            }
        }
        else
        {
            if ((i > 0) && cmp(i, (i-1)/2, boost::mpl::true_()))
            {
                swap(_queue[i], _queue[(i-1)/2]);
                bubble_up((i-1)/2, boost::mpl::true_());
            }
            else
            {
                bubble_up(i, boost::mpl::false_());
            }
        }
    }

    template <class IsMin>
    void bubble_up(size_t pos, IsMin is_min)
    {
        size_t i = pos;
        while (true)
        {
            if (i > 2) // has grandparent
            {
                size_t m = ((i-1)/2 - 1)/2;
                if (cmp(i, m, is_min))
                {
                    swap(_queue[m], _queue[i]);
                    i = m;
                }
                else
                {
                    break;
                }
            }
            else
            {
                break;
            }
        }
    }

private:
    std::vector<Value> _queue;
    Compare _cmp;
};


#endif // MINMAX_HH