/afs/cern.ch/work/a/aaltunda/public/www/CMSSW_6_2_5/src/PhysicsTools/JetMCUtils/interface/combination.h

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//=======================================================
// combination.h
// Description : Template class to find combinations
//=======================================================
// Copyright 2003 - 2006 Wong Shao Voon
// No warranty, implied or expressed, is included.
// Author is not liable for any type of loss through 
// the use of this source code. Use it at your own risk!
//=======================================================


#ifndef __COMBINATION_H__
#define __COMBINATION_H__


namespace stdcomb
{

// Non recursive template function
template <class BidIt>

inline bool next_combination(BidIt n_begin, BidIt n_end,
BidIt r_begin, BidIt r_end)
{
  
  bool boolmarked=false;
  BidIt r_marked;
  
  BidIt n_it1=n_end;
  --n_it1;
  
  
  BidIt tmp_r_end=r_end;
  --tmp_r_end;
  
  for(BidIt r_it1=tmp_r_end; r_it1!=r_begin || r_it1==r_begin; --r_it1,--n_it1)
  {
    if(*r_it1==*n_it1 )
    {
      if(r_it1!=r_begin) //to ensure not at the start of r sequence
      {
        boolmarked=true;
        r_marked=(--r_it1);
        ++r_it1;//add it back again 
        continue;
      }
      else // it means it is at the start the sequence, so return false
        return false;      
    }
    else //if(*r_it1!=*n_it1 )
    {
      //marked code
      if(boolmarked==true)
      {
        //for loop to find which marked is in the first sequence
        BidIt n_marked;//mark in first sequence
        for (BidIt n_it2=n_begin;n_it2!=n_end;++n_it2)
          if(*r_marked==*n_it2) {n_marked=n_it2;break;}
      
    
        BidIt n_it3=++n_marked;    
        for  (BidIt r_it2=r_marked;r_it2!=r_end;++r_it2,++n_it3)
        {
          *r_it2=*n_it3;
        }
        return true;
      }
      for(BidIt n_it4=n_begin; n_it4!=n_end; ++n_it4)
        if(*r_it1==*n_it4)
        {
          *r_it1=*(++n_it4);
          return true;           
        }
    }
  }  

  return true;//will never reach here    
}

// Non recursive template function with Pred
template <class BidIt, class Prediate>

inline bool next_combination(
        BidIt n_begin, 
        BidIt n_end,
        BidIt r_begin, 
        BidIt r_end,
        Prediate Equal)
{
  
  bool boolmarked=false;
  BidIt r_marked;
  
  BidIt n_it1=n_end;
  --n_it1;
  
  
  BidIt tmp_r_end=r_end;
  --tmp_r_end;
  
  for(BidIt r_it1=tmp_r_end; r_it1!=r_begin || r_it1==r_begin; --r_it1,--n_it1)
  {
    if( Equal( *r_it1, *n_it1) )
    {
      if(r_it1!=r_begin) //to ensure not at the start of r sequence
      {
        boolmarked=true;
        r_marked=(--r_it1);
        ++r_it1;//add it back again 
        continue;
      }
      else // it means it is at the start the sequence, so return false
        return false;      
    }
    else //if(*r_it1!=*n_it1 )
    {
      //marked code
      if(boolmarked==true)
      {
        //for loop to find which marked is in the first sequence
        BidIt n_marked;//mark in first sequence
        for (BidIt n_it2=n_begin;n_it2!=n_end;++n_it2)
          if( Equal( *r_marked, *n_it2) ) {n_marked=n_it2;break;}
      
    
        BidIt n_it3=++n_marked;    
        for  (BidIt r_it2=r_marked;r_it2!=r_end;++r_it2,++n_it3)
        {
          *r_it2=*n_it3;
        }
        return true;
      }
      for(BidIt n_it4=n_begin; n_it4!=n_end; ++n_it4)
        if( Equal(*r_it1, *n_it4) )
        {
          *r_it1=*(++n_it4);
          return true;           
        }
    }
  }  

  return true;//will never reach here    
}


// Non recursive template function
template <class BidIt>

inline bool prev_combination(BidIt n_begin, BidIt n_end,
BidIt r_begin, BidIt r_end)
{
  
  bool boolsame=false;
  BidIt marked;//for r
  BidIt r_marked;
  BidIt n_marked;
  

  BidIt tmp_n_end=n_end;
  --tmp_n_end;
  
  BidIt r_it1=r_end;
  --r_it1;
  
  for(BidIt n_it1=tmp_n_end; n_it1!=n_begin || n_it1==n_begin ; --n_it1)
  {
    if(*r_it1==*n_it1)
    {
      r_marked=r_it1;
      n_marked=n_it1;
      break;
    }
  }  
  
  BidIt n_it2=n_marked;


  BidIt tmp_r_end=r_end;
  --tmp_r_end;
  
  for(BidIt r_it2=r_marked; r_it2!=r_begin || r_it2==r_begin; --r_it2,--n_it2)
  {
    if(*r_it2==*n_it2 )
    {
      if(r_it2==r_begin&& !(*r_it2==*n_begin) )
      {
        for(BidIt n_it3=n_begin;n_it3!=n_end;++n_it3)
        {
          if(*r_it2==*n_it3)
          {
            marked=r_it2;
            *r_it2=*(--n_it3);
            
            BidIt n_it4=n_end;
            --n_it4;
            for(BidIt r_it3=tmp_r_end; (r_it3!=r_begin || r_it3==r_begin) &&r_it3!=marked; --r_it3,--n_it4)
            {
              *r_it3=*n_it4;              
            }
            return true;
          }
        }
      }
      else if(r_it2==r_begin&&*r_it2==*n_begin)
      {
        return false;//no more previous combination; 
      }
    }
    else //if(*r_it2!=*n_it2 )
    {
      ++r_it2;
      marked=r_it2;
      for(BidIt n_it5=n_begin;n_it5!=n_end;++n_it5)
      {
        if(*r_it2==*n_it5)
        {
          *r_it2=*(--n_it5);

          BidIt n_it6=n_end;
          --n_it6;
          for(BidIt r_it4=tmp_r_end; (r_it4!=r_begin || r_it4==r_begin) &&r_it4!=marked; --r_it4,--n_it6)
          {
            *r_it4=*n_it6;              
          }
          return true;
        }
      }
    }
  }  
  return false;//Will never reach here, unless error    
}


// Non recursive template function with Pred
template <class BidIt, class Prediate>

inline bool prev_combination(
        BidIt n_begin, 
        BidIt n_end,
        BidIt r_begin, 
        BidIt r_end,
        Prediate Equal)
{
  
  bool boolsame=false;
  BidIt marked;//for r
  BidIt r_marked;
  BidIt n_marked;
  

  BidIt tmp_n_end=n_end;
  --tmp_n_end;
  
  BidIt r_it1=r_end;
  --r_it1;
  
  for(BidIt n_it1=tmp_n_end; n_it1!=n_begin || n_it1==n_begin ; --n_it1)
  {
    if( Equal(*r_it1, *n_it1) )
    {
      r_marked=r_it1;
      n_marked=n_it1;
      break;
    }
  }  
  
  BidIt n_it2=n_marked;


  BidIt tmp_r_end=r_end;
  --tmp_r_end;
  
  for(BidIt r_it2=r_marked; r_it2!=r_begin || r_it2==r_begin; --r_it2,--n_it2)
  {
    if( Equal(*r_it2, *n_it2) )
    {
      if(r_it2==r_begin&& !Equal(*r_it2, *n_begin) )
      {
        for(BidIt n_it3=n_begin;n_it3!=n_end;++n_it3)
        {
          if(Equal(*r_it2, *n_it3))
          {
            marked=r_it2;
            *r_it2=*(--n_it3);
            
            BidIt n_it4=n_end;
            --n_it4;
            for(BidIt r_it3=tmp_r_end; (r_it3!=r_begin || r_it3==r_begin) &&r_it3!=marked; --r_it3,--n_it4)
            {
              *r_it3=*n_it4;              
            }
            return true;
          }
        }
      }
      else if(r_it2==r_begin&&Equal(*r_it2, *n_begin))
      {
        return false;//no more previous combination; 
      }
    }
    else //if(*r_it2!=*n_it2 )
    {
      ++r_it2;
      marked=r_it2;
      for(BidIt n_it5=n_begin;n_it5!=n_end;++n_it5)
      {
        if(Equal(*r_it2, *n_it5))
        {
          *r_it2=*(--n_it5);

          BidIt n_it6=n_end;
          --n_it6;
          for(BidIt r_it4=tmp_r_end; (r_it4!=r_begin || r_it4==r_begin) &&r_it4!=marked; --r_it4,--n_it6)
          {
            *r_it4=*n_it6;              
          }
          return true;
        }
      }
    }
  }  
  return false;//Will never reach here, unless error    
}


// Recursive template function
template <class RanIt, class Func>

void recursive_combination(RanIt nbegin, RanIt nend, int n_column,
                      RanIt rbegin, RanIt rend, int r_column,int loop, Func func)
{
        
        int r_size=rend-rbegin;
        
        
        int localloop=loop;
        int local_n_column=n_column;
        
        //A different combination is out
        if(r_column>(r_size-1))
        {
    func(rbegin,rend);
    return;
        }
        
        for(int i=0;i<=loop;++i)
        {
                                
                RanIt it1=rbegin;
                for(int cnt=0;cnt<r_column;++cnt)
                {
                  ++it1;
                } 
                
                RanIt it2=nbegin;
                for(int cnt2=0;cnt2<n_column+i;++cnt2)
                {
                  ++it2;
                } 
                
                *it1=*it2;
                
                ++local_n_column;
                
                recursive_combination(nbegin,nend,local_n_column,
                        rbegin,rend,r_column+1,localloop,func);
                --localloop;
        }
        
}

}

#endif