I don't see how your specification is solvable.

What output would you want on an input file of: 

10 a
10 b
11 c
11 d
18 e
19 f

[download]
A valid Huffman output has to look something like: 
a 10 000
b 10 001
e 18 01
c 11 100
d 11 101
f 19 11

[download]
There is simply no way to write a valid Huffman encoding of this example with the letters appearing sorted by weight. (In this representation e appears before c and d.)

In reply to Re (tilly) 1: A Golf question maybe? Huffman with a twist by tilly
in thread A Golf question maybe? Huffman with a twist by demerphq

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