src/utils/next_combination.hpp

/*
 * Copyright (C) 2000-2004  Object Oriented Parallel Simulation Engine (OOPSE) project
 * 
 * Contact: oopse@oopse.org
 * 
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public License
 * as published by the Free Software Foundation; either version 2.1
 * of the License, or (at your option) any later version.
 * All we ask is that proper credit is given for our work, which includes
 * - but is not limited to - adding the above copyright notice to the beginning
 * of your source code files, and to any copyright notice that you may distribute
 * with programs based on this work.
 * 
 * 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 Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 *
 */

/**
 * @file GenerateCombination.hpp
 * @author    tlin
 * @date  10/27/2004
 * @version 1.0
 */ 

#ifndef UTILS_NEXT_COMBINATION_HPP
#define UTILS_NEXT_COMBINATION_HPP

#include <vector>
#include <iterator>

namespace oopse {

/**
 * STL next_permuationtation like combination sequence generator 
 * 
 * <p> Preconditions: </p>
 * 
 */
template<class RandomAccessIterator, template<typename ELEM, typename = std::allocator<ELEM> > class IteratorContainer>
bool next_combination(IteratorContainer<RandomAccessIterator>& iterContainer, RandomAccessIterator first, RandomAccessIterator last) {
    if (first == last) {
        return false;
    }
    
    RandomAccessIterator endIter = --last;
    typename IteratorContainer<RandomAccessIterator>::iterator i = iterContainer.end();
    
    if (iterContainer.empty()) {
        //if sequence is empty, we insert the first iterator
        iterContainer.insert(iterContainer.end(), first);
        return true;
    } else if (*(--i) != endIter){
        //if the last iterator in iterContainer does not reaches the end, just increment it 
        ++(*i);
        return true;
    } else {// the last iterator in iterContainer does not reaches the end

        //starts at the end of the sequence and works its way towards the front, looking for two 
        //consecutive members of the sequence where the difference between them is greater 
        //than one. For example , if the sequence contains 1, 5, 8, 9 (total number is 10, begin
        //index is 0, therefore 9 is the end index, and the current size is 4). At the end of while
        //loop, j will point to 5, and i will point to 8, next combination should be 1, 6, 7, 8.
        //If j is less than zero, it means it already reaches the last combination of current size.
        //For instance, sequence may contain 6, 7, 8, 9 at this time, we need to increase the size
        // of combination to 5
        typename IteratorContainer<RandomAccessIterator>::iterator j = i;
        j--;
        while( j >= iterContainer.begin() && *i == *j + 1){
            i--;
            j--;
        };

        RandomAccessIterator raIter;
        if (j - iterContainer.begin() < 0) { //reaches the last combination of current size
            //half open range
            if (last  - first + 1  == iterContainer.size()) {
                //if the current size equals to total number, done
                return false;
            } else {

                //push the first currentSize+1 element into sequence 
                
                for(i = iterContainer.begin(), raIter= first; i  != iterContainer.end(); ++i, ++raIter) {
                    *i = raIter;
                }    
                iterContainer.insert(iterContainer.end(), raIter);
                
                return true; 
            }
            
        } else {
            ++(*j);
            raIter = *j;
            for(; i != iterContainer.end(); ++i) {
                ++raIter;
                *i = raIter;
            }
            return true;
        }
    }
} //end next_combination

} //end namespace oopse
#endif //UTILS_NEXT_COMBINATION_HPP

Revision:	1675
Committed:	Thu Oct 28 19:33:46 2004 UTC (19 years, 8 months ago) by tim
Original Path:	*trunk/OOPSE-2.0/src/utils/next_combination.hpp*
File size:	4293 byte(s)
Log Message:	Minor change
#	Content
1	/*
2	* Copyright (C) 2000-2004 Object Oriented Parallel Simulation Engine (OOPSE) project
3	*
4	* Contact: oopse@oopse.org
5	*
6	* This program is free software; you can redistribute it and/or
7	* modify it under the terms of the GNU Lesser General Public License
8	* as published by the Free Software Foundation; either version 2.1
9	* of the License, or (at your option) any later version.
10	* All we ask is that proper credit is given for our work, which includes
11	* - but is not limited to - adding the above copyright notice to the beginning
12	* of your source code files, and to any copyright notice that you may distribute
13	* with programs based on this work.
14	*
15	* This program is distributed in the hope that it will be useful,
16	* but WITHOUT ANY WARRANTY; without even the implied warranty of
17	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
18	* GNU Lesser General Public License for more details.
19	*
20	* You should have received a copy of the GNU Lesser General Public License
21	* along with this program; if not, write to the Free Software
22	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
23	*
24	*/
25
26	/**
27	* @file GenerateCombination.hpp
28	* @author tlin
29	* @date 10/27/2004
30	* @version 1.0
31	*/
32
33	#ifndef UTILS_NEXT_COMBINATION_HPP
34	#define UTILS_NEXT_COMBINATION_HPP
35
36	#include <vector>
37	#include <iterator>
38
39	namespace oopse {
40
41	/**
42	* STL next_permuationtation like combination sequence generator
43	*
44	* <p> Preconditions: </p>
45	*
46	*/
47	template<class RandomAccessIterator, template<typename ELEM, typename = std::allocator<ELEM> > class IteratorContainer>
48	bool next_combination(IteratorContainer<RandomAccessIterator>& iterContainer, RandomAccessIterator first, RandomAccessIterator last) {
49	if (first == last) {
50	return false;
51	}
52
53	RandomAccessIterator endIter = --last;
54	typename IteratorContainer<RandomAccessIterator>::iterator i = iterContainer.end();
55
56	if (iterContainer.empty()) {
57	//if sequence is empty, we insert the first iterator
58	iterContainer.insert(iterContainer.end(), first);
59	return true;
60	} else if (*(--i) != endIter){
61	//if the last iterator in iterContainer does not reaches the end, just increment it
62	++(*i);
63	return true;
64	} else {// the last iterator in iterContainer does not reaches the end
65
66	//starts at the end of the sequence and works its way towards the front, looking for two
67	//consecutive members of the sequence where the difference between them is greater
68	//than one. For example , if the sequence contains 1, 5, 8, 9 (total number is 10, begin
69	//index is 0, therefore 9 is the end index, and the current size is 4). At the end of while
70	//loop, j will point to 5, and i will point to 8, next combination should be 1, 6, 7, 8.
71	//If j is less than zero, it means it already reaches the last combination of current size.
72	//For instance, sequence may contain 6, 7, 8, 9 at this time, we need to increase the size
73	// of combination to 5
74	typename IteratorContainer<RandomAccessIterator>::iterator j = i;
75	j--;
76	while( j >= iterContainer.begin() && i == j + 1){
77	i--;
78	j--;
79	};
80
81	RandomAccessIterator raIter;
82	if (j - iterContainer.begin() < 0) { //reaches the last combination of current size
83	//half open range
84	if (last - first + 1 == iterContainer.size()) {
85	//if the current size equals to total number, done
86	return false;
87	} else {
88
89	//push the first currentSize+1 element into sequence
90
91	for(i = iterContainer.begin(), raIter= first; i != iterContainer.end(); ++i, ++raIter) {
92	*i = raIter;
93	}
94	iterContainer.insert(iterContainer.end(), raIter);
95
96	return true;
97	}
98
99	} else {
100	++(*j);
101	raIter = *j;
102	for(; i != iterContainer.end(); ++i) {
103	++raIter;
104	*i = raIter;
105	}
106	return true;
107	}
108	}
109	} //end next_combination
110
111	} //end namespace oopse
112	#endif //UTILS_NEXT_COMBINATION_HPP
113