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<TITLE>Permutations: Secret Santa</TITLE>
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<h1>Fixed-point-free Permutations: Secret Santa</h1>
      
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Secret Santa is a Western Christmas tradition 
<br>in which members of a group or community 
<br>are randomly assigned a person 
<br>to whom they give a gift. 
<br>(The identity of the gift giver remains secret.)

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This is a typical example for a permutation (the gifts are permuted).
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<br>Remember: not all permutations are fixed-point-free!
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This means: 
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The probability that someone gets back the own gift, is around 63 %,
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and this is nearly independent of the size of the group
<br>(even if all people from Shanghai would play the game).

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