i have a file like 
1300018   a1
1300019   a1
1300100   a2
1300101   a2
1300126   a2
1300127   a2
1300128   a2
1300129   a2
1300130   a3
1300131   a3
1300132   a3
1300133   a3

[download]
i want it to be like 
a1 2file
1300018 
1300019

a2 6file
1300100   
1300101   
1300126   
1300127   
1300128   
1300129   

a3 4file
1300130 
1300131  
1300132
1300133

[download]
i know i should use hash to deal with it... but after completed to assign key and value to hash....how to unique a1 column and make uniqued a1 column to corresponding to fist column?

In reply to question about algorithm by cxfcxf

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