algorithm - external sorting -

in web page:

merge resulting runs successively bigger runs, until file sorted.

as quoted, how can merge resulting runs together??? don't hava memory.

imagine have numbers 1 - 9

9  7  2  6  3  4  8  5  1

and let's suppose 3 fit in memory @ time.

so you'd break them chunks of 3 , sort each, storing each result in separate file:

279 346 158

now you'd open each of 3 files streams , read first value each:

2 3 1

output lowest value 1, , next value stream, have:

2 3 5

output next lowest value 2, , continue onwards until you've outputted entire sorted list.

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