kostka's blog

By kostka, 10 years ago, In English

Aren't you tired after Codeforces Round 282 (Div. 1)?

Did you know...

that when you will be on the list of "best hackers" of the round the row with your handle will be highlighted (if you will be logged in)?

Other posts can be found here, including div2.

Stats

Problem Successful hacks Unsuccessful hacks Other Sum Solutions which can be hacked Accepted solutions All solutions on final tests
494A - Treasure 363 (53.23%) 293 (42.96%) 26 (3.81%) 682 201 (23.40%) 658 (76.60%) 859
494B - Obsessive String 2 (50.00%) 2 (50.00%) 0 (0.00%) 4 32 (8.42%) 348 (91.58%) 380
494C - Helping People 0 0 0 0 6 (17.14%) 29 (82.86%) 35
494D - Birthday 0 0 0 0 1 (4.76%) 20 (95.24%) 21
494E - Sharti 0 0 0 0 0 (0.00%) 2 (100.00%) 2
Here should be graph.
Here should be graph.

Hacks and possible hacks description

494A - Treasure

First hack — 10 minutes after start of the contest, 363 hacked solutions and 201 more to hack!

The hacks were simple strings with no solutions like:

(#(
(((#)((
(#(()

It was also test #14 (look below):

((#)(

Pretty and deadly :)

Here should be graph.

494B - Obsessive String

Here are just congratulations for Alex_2oo8 for making two out of two hacks for this problem. Check them out: 129139 and 129164.

Here should be graph.

494C - Helping People

Here should be graph.

494D - Birthday

Here should be graph.

494E - Sharti

Here should be graph.

Fastest hackers

Problem Time Hacker Defender Hack
494A - Treasure 0:13:12 MrDindows I_love_Lindsay 127888
494B - Obsessive String 1:17:53 Alex_2oo8 PAP 129139

Best hackers

Hacker Stats Successful hacks Unsuccessful hacks
vitux +12-2 (1100) A: 127922 127927 127937 127960 127982 128054 128094 128481 128531 128773 128886 129815
A: 127913 128015
gchebanov +10-1 (950) A: 128356 128444 128524 128543 128549 128561 128578 128584 128673 128682
A: 128400
Egor +9-1 (850) A: 128027 128134 128279 128344 128371 128378 128404 128420 128466
A: 128391
mnbvmar +8-3 (650) A: 128722 128759 128777 128940 129154 129166 129232 129267
A: 128867 129024 129074
albertg +9-5 (650) A: 127901 127907 127920 127932 127983 128159 128302 128346 128685
A: 127965 128031 128472 128643 129402
linjek +12-11 (650) A: 127899 127957 128041 128097 128106 128193 128220 128340 128362 128857 128948 129117
A: 127924 127934 128035 128061 128133 128256 128312 129049 129251 129303 129337
Volkswagen +7-1 (650) A: 128010 128072 128120 128125 128188 128222 129436
A: 127999
TMandzu +8-4 (600) A: 128354 128375 128408 128417 128501 128535 128715 128745
A: 128525 128602 128875 128919
Dymonchyk +7-2 (600) A: 128512 128747 128769 128822 128870 128956 128979
A: 128616 129077
RAVEman +6-0 (600) A: 128155 128265 128335 128363 128450 128507

nic11 +8-4 (600) A: 127930 127940 127946 127953 127969 127987 128038 128049
A: 127961 128012 128068 128136
kraskevich +6-1 (550) A: 128766 128807 128820 128834 128994 129104
A: 129130
Swistakk +6-1 (550) A: 128402 128442 128447 128494 128508 128516
A: 129050
sokokaleb +5-0 (500) A: 128241 128289 128347 128407 128678

9charles +6-2 (500) A: 128296 128564 128585 129494 129689 129816
A: 128473 129425
sas4eka +5-0 (500) A: 127959 128100 128246 128423 128692

Bobgy +6-2 (500) A: 128093 128195 128291 128388 128479 128539
A: 128077 128463
Alex_2oo8 +6-2 (500) A: 127933 128043 128255 128306
B: 129139 129164
A: 128369 128406

qwerty787788 +5-0 (500) A: 128118 128184 128326 128368 129470

mateusz +6-2 (500) A: 128569 128628 128739 128776 128789 129116
A: 128601 128724
kostka +7-4 (500) A: 127966 128089 128113 128127 128194 128432 129551
A: 127926 128040 128414 129761
GlebWin +5-0 (500) A: 128088 128179 128227 129227 129770

Best rooms

Room #hacks Hackers
11 18 linjek [12], PERNEKHAN [2], Aeon [2], allllekssssa [1], oversolver [1]
2 17 9charles [6], nemzs [6], scfkcf [3], HolkinPV [1], Reyiz [1]
5 14 vitux [12], ImaDra [1], SAKT [1]
19 14 albertg [9], InheritG [2], xwind [2], pllk [1]
16 13 TMandzu [8], tomlau [3], Fantasy-zwj [1], agw [1]
4 12 qwerty787788 [5], sokokaleb [5], bernett [2]
10 12 Yury_Bandarchuk [5], GlebWin [5], EKGMA [1], kmjp [1]
32 12 nic11 [8], YakutovDmitriy [2], adiko2008 [2]
35 12 mbaros [7], alpq654323 [3], bayleef [2]
21 11 Swistakk [6], Na2a [3], Vladyslav [2]

Best countries

Yey for Poland for being here for the first time! :)

Country #hacks Hackers
Russia 75 linjek [12], gchebanov [10], Egor [9], nic11 [8], kraskevich [6], qwerty787788 [5], viktorov [5], Milanin [3], lkolt [2], YakutovDmitriy [2], zemen [2], bayleef [2], shilov [2], Lelby [1], HolkinPV [1], SirNickolas [1], oversolver [1], AndreySiunov [1], pitfall [1], VArtem [1]
Belarus 46 vitux [12], vilcheuski [7], nemzs [6], sas4eka [5], Yury_Bandarchuk [5], GlebWin [5], Arthur [3], tourist [3]
Ukraine 35 Dymonchyk [7], RAVEman [6], sdya [5], ballon [4], Maestr0 [4], vanchope [4], MrDindows [3], Vladyslav [2]
China 31 v-guihom [6], Bobgy [6], zscc [4], hiyot [3], InheritG [2], gantians [2], xwind [2], SIO__Five [2], 1A2012 [2], Fantasy-zwj [1], squee_spoon [1]
Poland 29 mnbvmar [8], kostka [7], mateusz [6], Swistakk [6], Keram [1], dj3500 [1]
Kazakhstan 19 Volkswagen [7], Na2a [3], Aeon [2], PERNEKHAN [2], adiko2008 [2], a_kabdygali [1], ImaDra [1], zhabo [1]
  • Vote: I like it
  • +42
  • Vote: I do not like it

»
10 years ago, # |
  Vote: I like it +4 Vote: I do not like it

Wow, I am honored. Egor unsuccessfully hacked my solution.

(of course, it proceeded to fail system tests)

»
10 years ago, # |
Rev. 2   Vote: I like it +3 Vote: I do not like it

Good job. We are waiting for div2 analysis.

  • »
    »
    10 years ago, # ^ |
      Vote: I like it +9 Vote: I do not like it

    I think another interesting statistic on this topic might be something like this: hacked solutions / (hacked solutions + failed systests) this will show how good were hackers in looking up all errors in other people's solutions.

    • »
      »
      »
      10 years ago, # ^ |
        Vote: I like it +6 Vote: I do not like it

      Yeah, really nice idea. I will implement it next time. It's partially shown on the second graph (accepted/rejected/hacked), but you are right, it will be better shown with numbers too.

      In this round it was: A: 64.36 % (nice!) B: 5.88 % C, D, E with 0%.

  • »
    »
    10 years ago, # ^ |
      Vote: I like it +6 Vote: I do not like it

    Sorry for delay, but it is done already here.

»
10 years ago, # |
  Vote: I like it +16 Vote: I do not like it

You should probably explain the two hacks on B, as well as that huge wrong answer spike on test 47: many solutions subtract 1 in the end, so they end up printing "-1" instead of "1000000006" for this case.

  • »
    »
    10 years ago, # ^ |
      Vote: I like it +20 Vote: I do not like it

    I'm interested how to come up with testcase that uncovers such bug :P.

    • »
      »
      »
      10 years ago, # ^ |
      Rev. 5   Vote: I like it 0 Vote: I do not like it

      Does anyone have an idea for this? I thought about locking this problem, because I thought some people might miss the subtraction with mods, but I couldn't find a good way to exploit it. It turned out no one in my room failed because of it, but still...

      Nevermind, I got it. First assume the string is of some convenient form, like bbb...b+acca+bbb...b (acca within a lot of b's), and the string to search for is "a". For this just try things (I tried a single "a" within before, and also "aca" within). Let there be x b's at the beginning and y b's at the end. Then, the answer is the sum of 3(x + 1) + 3(y + 1) for the one element sequences with 1 "a" and no "c"s, (x + 1)(y + 1) for the one element sequences with both "a"s, and 6(x + 1)(y + 1) for the two element sequences, giving 3(x + 1) + 3(y + 1) + 7(x + 1)(y + 1). W|A (why doesn't my link work? see below for link) gives integer solutions, for example x=3366,y=84845.

      This works:

      for (int i=0;i<3366;i++) printf("b");
      printf("acca");
      for (int i=0;i<84845;i++) printf("b");
      printf("\na\n");
      

      Try hacking this solution: 9106264.

      Go to wolframalpha.com and search 3*(x+1)+3*(y+1)+7*(x+1)*(y+1)=2000000013, 0<x<100000, 0<y<100000, x+y<100000.