This is a good puzzle not very tough to find solution of.
Puzzle : There are 3 standard on/off switches outside a room. One (and only one) controls a light bulb inside the room . The other two switches do nothing. You can only enter the room once, and cannot touch/change any switches after the door is open (or re-closed, for that matter). Damaging or disassembling the door, walls, or switches is against the rules.You can not see anything inside the room from outside in any way.Within these constraints, can you determine with certainty which switch controls the light bulb?
Have got some interview questions submit it here.So that we can help other candidates like you to land their dream job