a7mads3ed's blog

By a7mads3ed, history, 4 years ago, In English,

How can I solve Problem 275A ? http://codeforces.com/problemset/problem/275/A

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4 years ago, # |
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Consider a simpler problem:

Every time you press a light only the light pressed will be toggled.

Now it is obvious that if a light is pressed event number of times it will be in it's initial state (ON).

Now to solve the initial problem:

Let pressed[3][3] be the initial matrix and toggled[3][3] the matrix of total lamp presses.

In the beginning pressed[][] = toggled[][].

Now if pressed[i][j] != 0 then we have to add pressed[i][j] to toggled[i][j + 1], toggled[i][j - 1], toggled[i - 1][j] and toggled[i + 1][j]. Now we are left with the first, much simpler problem.

But be careful when handling edge lamps.

My solution (see how I handle edge lamps): http://codeforces.com/contest/275/submission/20742578

I hope I helped you.

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    4 years ago, # ^ |
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    Here is the same idea, but with different implementation. well, just consider it as another reference, haha :)


    Hope this helps :)

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    4 weeks ago, # ^ |
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    Thanks a lot, Buddy!