.. _sphx_glr_api_gallery_combinatorics_inclusion_exclusion:

Inclusion-exclusion
---------------------

The inclusion-exclusion principle and derangements.


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  <div id='sg-tag-list' class='sphx-glr-tag-list'></div>


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    <div class="sphx-glr-thumbnails">

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    <div class="sphx-glr-thumbcontainer" tooltip="n people check their hats and receive one back at random; what&#x27;s the probability nobody gets their own hat back? The answer converges to 1/e remarkably quickly.">

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  .. image:: /api/gallery/combinatorics/inclusion_exclusion/images/thumb/sphx_glr_plot_01_hat_check_problem_thumb.png
    :alt:

  :doc:`/api/gallery/combinatorics/inclusion_exclusion/plot_01_hat_check_problem`

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      <div class="sphx-glr-thumbnail-title">The hat-check problem: derangements via inclusion-exclusion</div>
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    </div>


.. toctree::
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   /api/gallery/combinatorics/inclusion_exclusion/plot_01_hat_check_problem