c-----------------------------------------------------------
c Chapter 3: Next k-subset of an n-set(p32)
c-----------------------------------------------------------
c   Name of subroutine: NEXKSB
c
c   Algorithm:Generating k-subset of {1,2,...,n} of an 
c             n-set, in lexicographical order. 
c
c-----------------------------------------------------------

c-----   The driver program is in nexksb_2.f   -------------

c-----Subroutine begins here--------------------------------
      subroutine nexksb(n,k,a,mtc)
      integer a(k),h
      logical mtc
      if(k.gt.0)goto 30
      do 1 i=1,n
 1    a(i)=0
      mtc=.false.
      return
   30 if(mtc) go to 40
   20 m2=0
      h=k
      go to 50
   40 if(m2.lt.n-h) h=0
      h=h+1
      m2=a(k+1-h)
   50 do 51 j=1,h
   51 a(k+j-h)=m2+j
      mtc=a(1).ne.n-k+1
      return
      end