Nvm, i interpreted it wrongly.
513426 doesnāt work then.
Yep, its not possible. My solution is wrong. 
Do you think the solution posted by the other guy is right ?
I got 90 for the first one but my other answers vary.I really havenāt checked his solution but he is my classmate (LOL) so i will discuss it with him tomorrow and let you know :).
I am pretty sure mine is correct, but you need to present the list in terms of E and L. Not sure what notation you are using
I need to get this right, otherwise my total is only 40 :\
I made two mistakes in sub questionsā¦
Mine was disproved. 513426 is not possible and I have counted it and many similar to it. So it is quite possible that yours is correct. My total is 50 but I am in 12th so I also am pretty scared that I might not appear for the second round.
I am in 12th as well. My total is 40 not including the second question; Iām pretty sure itās right so in that case itās 60.
Iām writing ZCO though so it should be okay.
Iāve written a brute-force algorithm to enumerate the possibilities.
The answers match up with what Iāve posted before.
Here is the program on ideone: kVLtjx - Online C++0x Compiler & Debugging Tool - Ideone.com
Below are the lists of sequences:
A: Dropbox - 2A.txt - Simplify your life
B: Dropbox - 2B.txt - Simplify your life
C: Dropbox - 2C.txt - Simplify your life
Edit: Note that E means Enter and L means Leave
http://textuploader.com/ob47 Q2a
http://textuploader.com/ob4v Q2b
http://textuploader.com/ob4n Q2c
Here are the corresponding final sequences. They appear to be right. Congrats.They match your text files line by line. @superty
Cool! Okay, so I have 60, most probably good enough to get to the next level.
Could you update the main post with all the corrected answers? Or you could write an answer and accept it.
Edit: Or I could do it, I need reputation so that I can comment on others posts 
@superty definitely good enough, My 50 marks are probably good enough. Add me as a friend on fb, iām in ronaqās friend list.(aditya puranik)
Added, Iām arjun
@rahulchhabra07 Do it the greedy way. Start making trips. Its meant to be done with pen and paper not a computer. Although I donāt see why a computer generated solution of brute force will be hard in this case. Think again and read the question multiple times. Iām sure you got confused. This is an easy question and one can easily score 20 marks in this. Even though I scored 10.
@Organic-Shilling well i did get 20, but my method was very time consuming. I created a table of every letter coming and the maximum flights to every position till then. this would finally give the maximum fights to get to 2. But is there any better algorithm?
Update:sorry, the answer is not 127, 123 is the highest
Point to the current airport with a pencil, read the next flight code and keep moving. The number of places where one has 2 choices are limited. In computer science terms be greedy while making decisions, where your greediness can foresee the next few airports and make change decisions accordingly.
Yep Confirmed. Congrats.
EDIT: By confirmed it means we have a list of all possible sequences and nobody has found a contradiction in them. See the comments of the answer on the top. Go through them, if you find a contradiction in a case or a missed case we are doomed.
@sidmohla 125346 is possible as --> 6 enters and leaves, 5 enters, 4 enters and leaves, 3 enters and leaves, 5 leaves, 2 enters and leaves, 1 enters and leaves. What are you final answers for this question.
Nobody knows the cut offs yet. But 30 for 11th seems reasonable to me.