StellarSpecter's blog

By StellarSpecter, history, 3 hours ago, In English

We all know, any permutation is made up of disjoint set of cyclic swaps. Read more about it here

i.e to make the permutation sorted, we need to do k-1 swaps for each k sized cycle.

Total swaps => n — number of cycles.

A variation of this standard problem was asked in the recent Div.3 2033E - Sakurako, Kosuke, and the Permutation,

We have to make the permutation such that either p[i] = i OR p[p[i]] = i ,

interestingly, solution to this comes as k/2-1 for each k sized cycle.

Now it makes me wonder what if we introduce one more condition to it =>

either p[i] = i OR p[p[i]] = i OR p[p[p[i]] = i

What would the answer be ? my intuition tells me it should be something in the order of k/6 for a cycle k.

Can you guys help me with this ?

Also what would be the general answer if we have m conditions like this,

either p[i] = i OR .... .... .... OR p[p[p[p[p[...i]....] = i .

Any help would be appreciated, Thanks!

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3 hours ago, # |
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i think it should be (n-m+1)/m for general case of m conditions.