keyence2020 d

keyence2020_d

Thoughts.

N=18

Since the operation can be repeated infinitely, first consider the "set reachable by repeating the operation"?

Is it subtle because it also requires a minimum number of times required?

Can repeat compatibility in any order

Flip over if it's an odd number away from the original position.

2^18 is less than 10^6, I'd say that's within the computable range of multiplying by 18.

No, it's a permutation, so 18!

If the constraints were not met when the first and second cards were set, they will not be met thereafter.

But you can't search while pruning branches with this, because it would be a full search in cases where everything has the same value.

This kind of case could be quickly obtained by finding the minimum value.

Official Explanation

I'm not sure of the specifics.

Minimum value of the operation when the already aligned set is msk and the last value is lst

The set of used values is 2^N, so express this in bits

I don't know if that is enough to keep the "monotonic increase" and add to it, so I'll hold the last card as well.

O(N 2^N)

https://gyazo.com/227ef044f17cd3088465d5c3121bc561

The order of operation is irrelevant.

---