test/utils/GenerateCombination.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_GENERATECOMBINATION_HPP
#define UTILS_GENERATECOMBINATION_HPP

#include <vector>

namespace oopse {
//this algorithm can be modified to be compatible with STL container
//Basically, changes totNum to last iteratir and beginIndex to first iterator, sequence from
//a vector<int> to a vector<iterator>, STL compatible version will be committed next time
bool next_combination(std::vector<int> sequence, int totNum, int beginIndex = 0) {
    int endIndex = beginIndex + totNum - 1;
    int currentSize;
    currentSize = sequence.size();
    
    if (currentSize == 0) {
        //if sequence is empty, we push the begin index into it
        sequence.push_back(beginIndex);
        return true;
    } else if (sequence[currentSize - 1] !=  endIndex) {
        //if the last element of the sequence does not reach the end index, just increment it 
        sequence[currentSize - 1] ++;
        return true;
    } else if (totNum == 1) {
        //if total number is one, and the last element already reaches the end index
        return false;
    } else {// At this point, the sequence contains at least two elements, and the last one already reaches
                // end index
        int i;
        int j;

        //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
        i = currentSize;
        j = i - 1;
        while( j >= 0 && sequence[i] == sequence[j] + 1){
            i--;
            j = i -1;
        };

        if (j < 0) { //reaches the last combination of current size

            if (currentSize == totNum) {
                //if the current size equals to total number, done
                return false;
            } else {

                //push the first currentSize+1 element into sequence 
                for(int i = 0; i < currentSize; i++)
                    sequence[i] = beginIndex + i;
                sequence.push_back(beginIndex + currentSize);
            }            
        } else {
            ++sequence[j];

            for(int k = j + 1; k < currentSize; k++)
                sequence[k] = sequence[k-1] + 1; 

        }
        
        
    }
    
}

} //end namespace oopse
#endif //UTILS_GENERATECOMBINATION_HPP
Revision:	171
Committed:	Thu Oct 28 06:16:45 2004 UTC (20 years, 6 months ago) by tim
File size:	4079 byte(s)
Log Message:	a STL next_permutaion like next_combination function.
#	User	Rev	Content
1	tim	171	/*
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_GENERATECOMBINATION_HPP
34			#define UTILS_GENERATECOMBINATION_HPP
35
36			#include <vector>
37
38			namespace oopse {
39			//this algorithm can be modified to be compatible with STL container
40			//Basically, changes totNum to last iteratir and beginIndex to first iterator, sequence from
41			//a vector<int> to a vector<iterator>, STL compatible version will be committed next time
42			bool next_combination(std::vector<int> sequence, int totNum, int beginIndex = 0) {
43			int endIndex = beginIndex + totNum - 1;
44			int currentSize;
45			currentSize = sequence.size();
46
47			if (currentSize == 0) {
48			//if sequence is empty, we push the begin index into it
49			sequence.push_back(beginIndex);
50			return true;
51			} else if (sequence[currentSize - 1] != endIndex) {
52			//if the last element of the sequence does not reach the end index, just increment it
53			sequence[currentSize - 1] ++;
54			return true;
55			} else if (totNum == 1) {
56			//if total number is one, and the last element already reaches the end index
57			return false;
58			} else {// At this point, the sequence contains at least two elements, and the last one already reaches
59			// end index
60			int i;
61			int j;
62
63			//starts at the end of the sequence and works its way towards the front, looking for two
64			//consecutive members of the sequence where the difference between them is greater
65			//than one. For example , if the sequence contains 1, 5, 8, 9 (total number is 10, begin
66			//index is 0, therefore 9 is the end index, and the current size is 4). At the end of while
67			//loop, j will point to 5, and i will point to 8, next combination should be 1, 6, 7, 8.
68			//If j is less than zero, it means it already reaches the last combination of current size.
69			//For instance, sequence may contain 6, 7, 8, 9 at this time, we need to increase the size
70			// of combination to 5
71			i = currentSize;
72			j = i - 1;
73			while( j >= 0 && sequence[i] == sequence[j] + 1){
74			i--;
75			j = i -1;
76			};
77
78			if (j < 0) { //reaches the last combination of current size
79
80			if (currentSize == totNum) {
81			//if the current size equals to total number, done
82			return false;
83			} else {
84
85			//push the first currentSize+1 element into sequence
86			for(int i = 0; i < currentSize; i++)
87			sequence[i] = beginIndex + i;
88			sequence.push_back(beginIndex + currentSize);
89			}
90			} else {
91			++sequence[j];
92
93			for(int k = j + 1; k < currentSize; k++)
94			sequence[k] = sequence[k-1] + 1;
95
96			}
97
98
99			}
100
101			}
102
103			} //end namespace oopse
104			#endif //UTILS_GENERATECOMBINATION_HPP