| Puzzle n°- Traverse through 100 doors, find which are open/closed ** [message #614731] |
Mon, 26 May 2014 11:07  |
Lalit Kumar B
Messages: 3174
Registered: May 2013
Location: World Wide on the Web
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Problem: You have 100 doors in a row that are all initially closed. You make 100 passes by the doors. The first time through, you visit every door and toggle the door (if the door is closed, you open it; if it is open, you close it). The second time you only visit every 2nd door (door #2, #4, #6, ...). The third time, every 3rd door (door #3, #6, #9, ...), etc, until you only visit the 100th door.
Question: Write a SQL to determine what state are the doors in after the last pass? Which are open, which are closed?
The doors can be considered as rown in table. A flag could be used as a column to store the status open/close.
P.S. : It has had been one of the favorite questions in management exams in the logical reasoning section.
Regards,
Lalit
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