how to get all different values for each key

[Jianxin Wang]

HI,
    I hava many <key,value> pairs now, and want to get all different values
for each key, which way is efficient for this work.

   such as input : <1,2> <1,3> <1,4> <1,3> <2,1> <2,2>
   output: <1,2/3/4> <2,1/2>

   Thanks!

walter