AnalysisCombination.h

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/*
  Copyright (C) 2002-2017 CERN for the benefit of the ATLAS collaboration
*/
 
#ifndef ANALYSISUTILS_ANALYSISCOMBINATION_H
#define ANALYSISUTILS_ANALYSISCOMBINATION_H

 
#include <vector>
 
namespace AnalysisUtils {

  template <class COLL> class Combination {
 
  public:

    Combination(COLL *coll, const unsigned int nElement);
    
    ~Combination() {}

    void reset();

    template <class OUT>
    bool get(OUT &comb)
    {
      // init returned combination
      comb.clear();
      
      if (m_first) {
    if (m_index[m_nElement-1] >= m_coll->size()) return false;
    m_first = false;
      } else {
    // increment indices
    if (!setNewIndex(m_nElement-1)) return false;
      }
      
      // assign to returned combination
      for (unsigned int i=0; i<m_nElement; ++i)
    comb.push_back((*m_coll)[m_index[i]]);
      
      return true;
    }

    template <class CALLER, class OUT, class CRITERIA>
    bool goodOnes(CALLER *caller, OUT &comb, CRITERIA criteria)
    {
      bool ret = get(comb);
      if (!ret) return false;
 
      // check if this passes the criteria
      if (criteria(caller, comb)) return true;
 
      // if not, look for next combination
      return goodOnes(caller, comb, criteria);
    }

    template <class OUT>
    bool get(OUT &comb, OUT &remain)
    {
      // init returned vector
      remain.clear();
 
      bool ret = get(comb);
      if (!ret) return false;
 
      // assigin to remain
      unsigned int sIndex = 0;
      std::vector<unsigned int>::const_iterator it  = m_index.begin();
      std::vector<unsigned int>::const_iterator itE = m_index.end();
      for (; ; ++it)
    {
      unsigned int eIndex;
      if (it!=itE)
        eIndex = *it;
      else
        eIndex = m_coll->size();
 
      for (unsigned int i=sIndex; i<eIndex; ++i)
        remain.push_back((*m_coll)[i]);
      sIndex = eIndex+1;
 
      if (it == itE) break;
    }
 
      return true;
    }

    template <class CALLER, class OUT, class CRITERIA>
    bool goodOnes(CALLER *caller, OUT &comb, OUT &remain, CRITERIA criteria)
    {
      bool ret = get(comb, remain);
      if (!ret) return false;
 
      // check if this passes the criteria
      if (criteria(caller, comb)) return true;
 
      // if not, look for next combination
      return goodOnes(caller, comb, remain, criteria);
    }
 
  private:

    COLL *m_coll;
    
    const unsigned int m_nElement;

    std::vector<unsigned int> m_index;

    bool m_first;

    bool setNewIndex (int iElement);
  };
 

  //  implementation
 
  template <class COLL> inline Combination<COLL>::Combination(COLL *coll, const unsigned int nElement)
    : m_coll(coll), m_nElement(nElement), m_first(true)
  {
    // init indices
    //    internal indices are [0,1,2...] at beginning 
    for (unsigned int i=0; i<nElement; ++i)
      m_index.push_back(i);
  }
  
  template <class COLL> inline void Combination<COLL>::reset()
  {
    // reset indices
    m_index.clear();
    for (unsigned int i=0; i<m_nElement; ++i)
      m_index.push_back(i);
 
    // set first flag
    m_first = true;
  }
 
  // iElement runs over 0..(m_nElement-1)
  template <class COLL> inline bool Combination<COLL>::setNewIndex (int iElement)
  {
    if (iElement < 0) return false;
    
    if (iElement+1 == static_cast<int>(m_nElement))
      {
    if ((m_index[iElement]+1) < m_coll->size())
      {
        ++(m_index[iElement]);
        return true;
      }
      }
    else
      {
    if ((m_index[iElement]+1) < m_index[iElement+1])
      {
        ++(m_index[iElement]);
        return true;
      }
      }
    
    if (setNewIndex (iElement-1))
      {
    m_index[iElement] = m_index.at(iElement-1)+1;
    return true;
      }
    
    return false;
  }
 
} // end of AnalysisUtils
 
#endif // END OF ANALYSISTOOLS_ANALYSISCOMBINATION_H