## Find the lights which are turn on.

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Find the lights which are turn on.
# 1
07-01-2010
Find the lights which are turn on.

See the interview question from other site, that I'd like to implement by AWK.

The rules are:

There are 100 lamps, number from 1 to 100. Initially, all of them are returned off.
First time, if the number of lamp is multiple by one, switch the lamp status; that's mean, if it turn off, turn it on, vice versa.
Second time, if the number of lamp is multiple by two, switch the lamp status;
Third time, if the number of lamp is multiple by three, switch the lamp status;
And so on, until find out the number of lamp is multiples of 100, switch the lamp status;

Finally list all number of lamps which turn on.

I write the code, but seems the var in Function is not public var. array a 's value can't be used outside of function.

How can I fix it?
 rdcwayx View Public Profile for rdcwayx Find all posts by rdcwayx
# 2
07-01-2010
Something like this?
This User Gave Thanks to Klashxx For This Post:
 Klashxx View Public Profile for Klashxx Find all posts by Klashxx
# 3
07-01-2010
I don't know the answer, but it is interesting, your results are some regular numbers, all of them are square numbers.

When I run your code in my system, I don't get any output. Try to understand your idea first.
 rdcwayx View Public Profile for rdcwayx Find all posts by rdcwayx
# 4
07-01-2010
Klashxx's result is correct. However, a more efficient way of calculating the result would be:

If you think about the problem (forget about the code, just think about the math), every single time that a lamp's id number is divisible by a number x, there will be another number, y, less than or equal to the number of lamps, by which it will also be divisible. So, for each x that toggles the lamp's state, there is a y which will undo its effect ... except when x=y, a square root.

Regards,
Alister

Last edited by alister; 07-01-2010 at 03:00 PM..
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# 5
07-02-2010
Very , very smart Alister !!
 Klashxx View Public Profile for Klashxx Find all posts by Klashxx

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