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From: jean-marc.alliot@irit.fr
To: caml-list@inria.fr
Subject: [Caml-list] Choosing a random element in a Map or a Set
Date: Thu, 18 Mar 2021 10:44:39 +0100
Message-ID: <3e61c49d-8b20-378b-0c24-75b8da14b4f7@alliot.org> (raw)

Dear list,

I am trying to take a random element from a Map or a Set.

Currently, I generate one random int between 1 et Card(map), and I iter
until I reach this element. The solution is in O(n) which is not great...

I was about to code the following solution: take the current Map code
and add a function which follows the balanced binary tree from the root
and takes randomly a left or right turn at each node until we reach a
leaf (we only need to generate one random int and use its binary
representation to choose the left or right direction at each node). This
should be in O(log(n))

Before I start coding like an idiot:
1) Is there another, more intelligent, solution?
2) Is my solution biased? I think it is not, as long as the tree is
properly balanced but...

Thanks

Jean-Marc



             reply	other threads:[~2021-03-18  9:41 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-18  9:44 jean-marc.alliot [this message]
2021-03-18 10:06 ` François Pottier
2021-03-18 14:20   ` Simon Cruanes
2021-03-18 17:06     ` jean-marc.alliot
2021-03-18 11:10 ` Nicolas Barnier
2021-03-18 11:32   ` François Pottier
2021-03-19  1:32   ` Francois Berenger
2021-03-18 12:34 ` Ivan Gotovchits
2021-03-18 12:48 ` Ivan Gotovchits

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