IOIPRAC INOI : What's the expected approach for Calvin's Game ?

dynamic-programming

#1

Whats the expected approach for Calvin’s Game INOI 13

My approach of choosing max(forwardphase_at_i + Reverse_At_i) apparently fails…


#2

DP Solution: Compute the following quantities#


$Forward*$ = $Max$ $score$ $if$ $we$ $move$ $forward$ $from$ $K$ to $i$, $for$ $all$ $K <= i <= N$

Backward* = Max score if we move backward from i to 1, for all K <= i <= N

Ans = Max (Forward* + Backward*) for all K <= i <= N

Make sure to include the case in which you don’t move forward at all.


(http://paste.ofcode.org/t3F82vBwPyPtkVybbpJWjD)

#3

I have a doubt. May be the doubt is silly

if the input is
5 2

5 3 -2 1 1 (sample input) then we can continuously increase our score by from 3 to 1 and then 1 to 3 repeatedly (here 3 refers to the number 3 and not the third position)… I probably didnt read the question properly but pls clarify this doubt.


#4

We can only one forward phase(not move) followed by one backward phase. If you go from 3 to 1 and come back to three you have completed the forward phase and cannot go forward any more.


#5

That’s very generous ,Thank You Very much, Now I know what I missed :slight_smile: :slight_smile:


#6

There’s also a simple enough graph side of things.


#7

thanks!!!