Problem 42498. Pancake sorting - minimum flips.

Created by Jan Orwat

Solve Later

Sort a stack of pancakes by flipping them using spatula.
There are N pancakes with diameters 1:N.
Spatula can be inserted anywhere in the stack and used to flip all the pancakes above.
Sort pancakes in increasing order.
Return a vector of places where spatula was inserted.
Minimize number of flips, your score will depend on the number of flips in the last few tests.
References: math.illinois.edu, wikipedia.
Example (horizontal view):
Initial stack:  6 4 2 5 3 1,         ("," indicates position of spatula)
first flip:     1 3 5,2 4 6
second:         5 3 1 2 4,6
...             4 2 1 3,5 6
                3 1 2,4 5 6
                2 1,3 4 5 6
sorted!         1 2 3 4 5 6
positions of spatula from the begining: 6 3 5 4 3 2

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69 Solutions
27 Solvers

Last Solution submitted on Jul 28, 2023

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Muthu Annamalai on 7 Aug 2015

William Gates and Christos Papadimitrou solved this problem, before the former left to co-found Microsoft. Very interesting problem indeed.

Lincoln Poon on 18 Oct 2022

Is the scoring system still working?

Dyuman Joshi on 18 Oct 2022

Lincoln, I checked the reference solution and it showed that the manual scoring system no longer works.
I will see what changes I can do and notify it here.

Stefan Abendroth on 26 May 2023

Unfortunately, the scoring system is broken (same as in the TRON challenge by Alfonso).
No way to get the Indexing IV badge :-(

Dyuman Joshi on 26 May 2023

@Stefan, I have commented out the part that outdated and the test suite is working now.

I have rescored your solution, you can now (hopefully) get the Indexing IV badge!

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