MathGroup Archive 2005

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reducing the time of constructing a List

please, what is the best way to reduce the timing of the following lines, the 
source of data is:
dat = Table[Random[Integer, {0, 10}], {100000}];
and the purpose is to construct the List lst in the following way:
For[i = 1, i <= 100000,
      If [dat[[i]] == 1,
        lst = Join[lst, {1}], lst = Join[lst, {0}]]; i++]; // Timing

Out[]= {226.07 Second, Null}
on the P4 celeron 2 Ghz , memory 382 MB ram

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