We invite you to participate in CodeChef’s Starters 97, this Wednesday, 5th July, rated till 6-stars Coders (ie. for users with rating < 2500).
Time: 8:00 PM — 10:00 PM IST
Note that the duration is 2 hours. Read about the recent CodeChef changes here.
Joining us on the problem setting panel are:
Setters: Yash yash_daga Daga, Nishank IceKnight1093 Suresh, Kanhaiya notsoloud1 Mohan, Ram grayhathacker Gopal Pandey, Ronit ro27 Bhatt, rainb0ysimp rainb0ySimp, Ziad ZiadEl-Gafy Waleed, Anirudh Chimpanzee
Testers: Jay JaySharma1048576 Sharma
Statement Verifier: Kanhaiya notsoloud1 Mohan
Video Editorialists: Sundar K Letscode_sundar,Madhav jhamadhav Jha, Jwala jwalapc , Rohit ezo_tihor Oze, Adhish ak2006 Kancharla
Text Editorialists: Nishank IceKnight1093 Suresh
Contest Admin: Yash yash_daga Daga
Written editorials will be available for all on discuss.codechef.com. Pro users can find the editorials directly on the problem pages after the contest.
The video editorials of the problems will be available for all users for 1 day as soon as the contest ends, after which they will be available only to Pro users.
Also, if you have some original and engaging problem ideas, and you’re interested in them being used in CodeChef's contests, you can share them here.
Hope to see you participating. Good Luck!
hope to reach 5*
hope not to lose it
Hope to reach 5*
Reminder: Contest starts in 3.5 hours.
It's 5:30 for me
Hope to reach expert in this contest 💀
Hoping for great problem statements.
Hoping for 5 star. This may be my last ever cc contest. Finger crossed
Hurray...!!!A contest made by alumni of my college.... looking forward to a great round and hope to reach 5 star.
great round
CodeChef_admin Hi, on the official website the editorial is pointed to START86 instead of START97.
Thanks for pointing this out. Fixed.
i wasted an hour on "Triplets Min" as I have used unsigned long long instead of long long because the constraints given are Ai>10^-9. But there are negative integers in test data
Yikes, apologies. It was meant to be -10^9. It's changed now.
I managed to solve Disappearing Domino Game in contest in $$$O(n ^ 2)$$$ with an incorrect greedy solution.
I found who wins in a normal game (where $$$D = \infty$$$) simply using Sprague-Grundy. Then I implemented how the game would go and counted its duration (by checking if xor of independent games becomes $$$0$$$). If there were mupltiple choices for a move, I just selected the first one. If the duration is $$$\ge D$$$, this is a draw, otherwise output what Sprague-Grundy says.
I then tried to stress-test it, but it passed all the random cases. I bruteforced small testcases and found that the smallest one which makes it fail is the following:
My solution only managed to finish the game in $$$7$$$ moves, while it is apparently possible to do that in $$$5$$$. I didn't find any failing tests with an advantage to Bob, so maybe it is always optimal to choose the first move if you're losing (which seems kinda logical, because you wanna prolong the game as much as possible), but maybe it is just a matter of size.
I also found the smallest tests for $$$k = 3$$$ and $$$k = 4$$$, but they are all simular:
UPD: I also found a test where Bob wins from the beginning. Alice can force a game to last $$$12$$$ moves, but making the first possible move can only achieve $$$10$$$.