<story><title>100 prisoners problem</title><url>https://en.wikipedia.org/wiki/100_prisoners_problem</url></story><parent_chain><item><author>dbatten</author><text>I&amp;#x27;m confused...&lt;p&gt;&amp;quot;Before the first prisoner enters the room, the prisoners may discuss strategy—but may not communicate once the first prisoner enters to look in the drawers.&amp;quot;&lt;p&gt;And, in the example given, &amp;quot;That prisoners 5 to 8 will also find their numbers can also be derived from the information gained by the first three prisoners.&amp;quot;&lt;p&gt;There&amp;#x27;s never any explanation of what happens when a prisoner opens a drawer and finds it empty. In the first example given, what happens when prisoner 5 goes in and there&amp;#x27;s nothing in drawer 5? The algorithm doesn&amp;#x27;t seem to account for this.&lt;p&gt;It seems like there&amp;#x27;s some sort of assumption that the later prisoners are gathering information from the earlier prisoners, but the problem set-up seems to preclude this? They&amp;#x27;re going into a room so they can&amp;#x27;t watch each other, the drawers are closed afterwards so they can&amp;#x27;t derive information from which drawers are open&amp;#x2F;closed, and they&amp;#x27;re not allowed to communicate.&lt;p&gt;Am I not following something?</text></item></parent_chain><comment><author>dbatten</author><text>Two things:&lt;p&gt;1) You don&amp;#x27;t take your number when you find it. I guess my brain assumed &amp;quot;find&amp;quot; meant &amp;quot;find and take with you to prove you found it.&amp;quot; Perhaps a better term might be &amp;quot;encounter.&amp;quot;&lt;p&gt;2) Here&amp;#x27;s a much better explanation (thanks micaeked): &lt;a href=&quot;http:&amp;#x2F;&amp;#x2F;datagenetics.com&amp;#x2F;blog&amp;#x2F;december42014&amp;#x2F;index.html&quot; rel=&quot;nofollow&quot;&gt;http:&amp;#x2F;&amp;#x2F;datagenetics.com&amp;#x2F;blog&amp;#x2F;december42014&amp;#x2F;index.html&lt;/a&gt;. Essentially, the algorithm works because following numbers to drawers will eventually create a loop (e.g., drawer 2 points to 4 points to 6 points to 2). By starting with the drawer with your number, you&amp;#x27;re guaranteed to be in a loop with your number. The only question is whether your loop is less than 50 drawers long...&lt;p&gt;Furthermore, this confirms that there IS no transfer of information from previous prisoners in any way.</text></comment>
<story><title>100 prisoners problem</title><url>https://en.wikipedia.org/wiki/100_prisoners_problem</url></story><parent_chain><item><author>dbatten</author><text>I&amp;#x27;m confused...&lt;p&gt;&amp;quot;Before the first prisoner enters the room, the prisoners may discuss strategy—but may not communicate once the first prisoner enters to look in the drawers.&amp;quot;&lt;p&gt;And, in the example given, &amp;quot;That prisoners 5 to 8 will also find their numbers can also be derived from the information gained by the first three prisoners.&amp;quot;&lt;p&gt;There&amp;#x27;s never any explanation of what happens when a prisoner opens a drawer and finds it empty. In the first example given, what happens when prisoner 5 goes in and there&amp;#x27;s nothing in drawer 5? The algorithm doesn&amp;#x27;t seem to account for this.&lt;p&gt;It seems like there&amp;#x27;s some sort of assumption that the later prisoners are gathering information from the earlier prisoners, but the problem set-up seems to preclude this? They&amp;#x27;re going into a room so they can&amp;#x27;t watch each other, the drawers are closed afterwards so they can&amp;#x27;t derive information from which drawers are open&amp;#x2F;closed, and they&amp;#x27;re not allowed to communicate.&lt;p&gt;Am I not following something?</text></item></parent_chain><comment><author>ajanuary</author><text>The numbers are left in the drawers once someone finds their number.</text></comment>