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POpython algorithm: how to efficiently find if two integer sets are intersected?
 

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  1. POpython algorithm: how to efficiently find if two integer sets are intersected?
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    <p>Given a set [2004, 2008], what is the fastest way to find if this set is intersected with other sets?</p> <p>Actually I am dealing a problem with database, the table has 2 columns, one is the lower bound, the other one is the higher bound. The task is to find all the intersected rows with the given 2 tuple(like [2004,2008]).</p> <p>I am using mongodb, is this intrinsically supported(I mean have keywords to do it). I have large user base, so I want this task to be completed as fast as possible.</p> <p>EDIT: To stat more clear, a database table contains following rows:</p> <pre><code>20 30 10 50 60 90 ... </code></pre> <p>Given the input <code>(25 40)</code> range, I want to return the rows which represent a range, have intersection with the given range.</p> <p>so return is: <code>(20 30),(10 50)</code></p>
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    1. USBin Chen
    1. USBin Chen
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    1. COIt is unclear from the way you've stated this, if you have *pairs* of values each pair representing range, and you want to know if any pair interesects, or you have two large set of values to intersect. Do you know anything about the size of the integers?
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      1. USIra Baxter
    2. COI don't know MongoDB at all, but you're basically looking for `SELECT * from the_table where not (lower_bound > 2008 or upper_bound < 2004)`. If it can't do that, it's not a database ;-p
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      1. USSteve Jessop
    3. CO@Steve Yes, actually this is the answer!! please write your comment into an answer and then I can accept it, thanks!
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      1. USBin Chen
 

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