N bulbs in a circle


There are n bulbs in a circle, each bulb has one switch associated with it, on operating the switch, it toggles the state of the corresponding bulb as well as two bulbs adjacent to that one. Given all bulbs are in off state initially, Give a situation when we can turn on all the bulbs.

Note: Number of bulbs are more then 1 i.e N>1

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    Every bulb can be switched by its previous bulb,by itself and by bulb following it .
    So if we switch all bulbs sequentially,a bulb in between changes its state 3 times,which results in chng of its state from initial(3%2=1).
    If all bulbs are switched from 1 to n sequentially all bulbs, including 1 and n
    change there state .
    Therefore to switch all bulbs on we only need to switch them on sequentially,
    irrespective of their n value.

    satyen Guru Answered on 28th July 2015.
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