查看完整版本: 【Brain Teaser】Mail（慈善杀手 解）

【Brain Teaser】Mail（慈善杀手 解）

<P>Two friends, Denis and Léo wish to communicate by mail.The mailman is dishonest. He steals. Each of the two friends has his own lock and key. They put their mail in a secure box.


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<P><B>Question: </B>How can Denis send a  letter to Léo without the mailman opening the box?
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[align=right][color=#000066][此贴子已经被作者于2004-6-23 13:44:54编辑过][/color][/align]

1 Denis puts the letter in the box, locks it and sends it to Leo.</P>2 Leo puts his lock on the box and sends the box back to Denis.<p></p></P>3 Denis unlocks his own lock from the box and sends the box to Leo.<p></p></P>4 Leo unlocks the lock from the box and gets the letter.<p></p></P>

<P>BINGO!</P><P>Denis sends a locked box with his letter to Leo.
Leo adds his lock to the box and returns it to Denis.
Denis gets the box, removes his lock and returns it to Leo.
Leo can now open box safely that has his lock on it. </P>