title: To find combination of a list
body: <p>i'm implementing Apriori algorithm. and i need to calculate the combination of a list 
  for example i have a list containing 
  ABC
  DEF
  GHI
  JKL
  and its out put should be like this
  ABCDEF
  ABCGHI
  ABCJKL</p>
  
  <p>plz tell me that hw i can get the output like this.....</p>