TCO22 Algorithm Competition Round 1A

It's that time again and we are excited! The first Online Round of the 2022 Topcoder Open Algorithm Competition has arrived and is open to all!

Details:

Up to 750 of the highest scorers from each Round 1 will advance to Round 2 of the Algorithm Competition.

If you're unable to make it or don't advance, there will be one more Round 1 — Round 1B on Wednesday, April 27, 2022 at 07:00 UTC -4.

Best of luck to you in the Arena!

PS: Please help our research friends with this survey if you have time! Takes a few minutes!

- The Topcoder Community Team

• 32 hours ago, # ^ |

  The list of the 250 people with round 1 byes is here: https://tco22.topcoder.com/competition/algorithm?tracks[algorithm-tabs]=4

  (scroll down a little to the "Automatic Berths aka Byes" section)

• 22 hours ago, # ^ |

  I think the 2500 limit is related to how much the server can handle and it's rarely, if ever, an issue. The parallel round is for the people who get to skip round 1 (e.g. they are very highly rated so they are auto-qualified for round 2). And based on previous years, I expect it to be rated!

• 18 hours ago, # ^ |

  Only 320 registered with less than half hour to go, so the 2500 limit is very theoretical.

  In fact, I'm trying to remember when a TCO round had more registrants than the cutoff for advancing. (Currently the cutoff is 750 so everybody who gets any points will advance).

  It's been like that for some years... Unfortunately, Topcoder destroyed their wonderful CP community. Still a good place though.

• 19 hours ago, # ^ |

  Please email support at [email protected] with details so they can help you out.

• 18 hours ago, # ^ |

  Division leaderboard still doesn't work in webarena.

• 16 hours ago, # ^ |

  ← Rev. 2 →  

  +86

  Is it intended, that the following strategy exists?

  -Open 250

  -Read 250

  -Solve 250

  -Submit 250

  -Read 1000's title

  -Solve 1000

  -Open 1000

  -Submit 1000

• 17 hours ago, # ^ |

  ← Rev. 2 →  

  +4

  After the challenge phase is over :)

  Edit: now that it is, here's the draft of the editorial

  • 16 hours ago, # ^ |

    Nice problem. I got the DP part to calculate pA & pB but didn't know the technique of writing an equation for probability "p" in terms of itself, to simulate the infinite process, and then solving for "p". Very nice general technique to know:

    p = pA*1 + pB*pA*1 + pB*pB*0 + (1-pA-pB*pA-pB*pB)*p

    In that equation, what do the "*1" and "*0" indicate? I'm familiar with multiplying probabilities by values to compute expected value, but unclear what probabilities the "1" and "0" represent here.

    (I liked the 250 also — thank you for making it a little bit harder than a division-2 250, as we have had in many recent TCO opening rounds. This was more like a division-2 450 so everybody had a chance but took a little thought).

    • 10 hours ago, # ^ |

      You are writing an expression for the probability that Alice wins. Whenever you reach a state where she has already won, she wins from that state with probability 1. And whenever you reach a state where she has already lost, she wins from that state with probability 0. That's where the 1 and 0 in this formula come from.

      • 9 hours ago, # ^ |

        Excellent.. so, including the *0 along with the *1 thus allows us to explicitly enumerate all the possible outcomes (both positive and negative), without missing one by accident. Thanks!

• 16 hours ago, # ^ |

  Seem lower constraint make the problem harder :)