Welcome back to Hack me! blog!
You asked for it, and you have it. After over one year I am back with short description of the best hackers and the most common hacks in Codeforces Round. The formula is quite new and poorer than before, I should say. I left only the most important messages.
If you are not familliar with the series, you may check my first post about it or all posts. ### Codeforces Round 346 (Div. 2)
All hacks
| problem / verdict | HACK_SUCCESSFUL | HACK_UNSUCCESSFUL | OTHER |
|---|---|---|---|
| A. Round House | 662.0 | 324.0 | 23.0 |
| B. Qualifying Contest | 315.0 | 137.0 | 64.0 |
| C. Tanya and Toys | 29.0 | 25.0 | 29.0 |
| D. Bicycle Race | 0.0 | 4.0 | 21.0 |
| E. New Reform | 1.0 | 5.0 | 1.0 |
| F. Polycarp and Hay | 1.0 | 7.0 | 2.0 |
This round was really hacker-friendly, as you may see a lot of hacks on A and B. As always, OTHER mean one of INVALID_INPUT, GENERATOR_CRASHED or GENERATOR_INCOMPILABLE.
Best hackers
Below is the least of people with hack score of at least 800 points. Congratulations to them!
| hacker | score | HACK_SUCCESSFUL | HACK_UNSUCCESSFUL |
|---|---|---|---|
| dImak24 | 1250.0 | 13.0 | 1.0 |
| jerjerinmylefthand | 1200.0 | 13.0 | 2.0 |
| albertg | 1150.0 | 13.0 | 3.0 |
| avamsi | 1100.0 | 11.0 | 0.0 |
| AlphaGo | 1050.0 | 12.0 | 3.0 |
| OmaeWaMouShenDeiru | 1050.0 | 11.0 | 1.0 |
| StrangeName | 900.0 | 9.0 | 0.0 |
| khaledA | 900.0 | 10.0 | 2.0 |
| ooyeln269 | 900.0 | 10.0 | 2.0 |
| Aviously | 900.0 | 10.0 | 2.0 |
| mr_justadog | 800.0 | 9.0 | 2.0 |
| SirNickolas | 800.0 | 8.0 | 0.0 |
And now let's take a look at some of their hacks, shall we? I decided to take dImak24 and jerjerinmylefthand hacks, because they show almost all tricky cases.
Edit: you may now click on id of the hack.
| id | hacker_handle | defender_handle | problem_name | test | judge_result |
|---|---|---|---|---|---|
| 223422 | dImak24 | chernyavskiy.dmitriy | A. Round House | 6 1 -2\r\n\n | WRONG_ANSWER |
| 223481 | dImak24 | akjain | A. Round House | 6 1 -100\r\n\n | WRONG_ANSWER |
| 223508 | dImak24 | chernyavskiy.dmitriy | A. Round House | 6 1 -100\r\n\n | WRONG_ANSWER |
| 223534 | dImak24 | miss_invictus | A. Round House | 6 1 -100\r\n\n | WRONG_ANSWER |
| 223542 | dImak24 | harish02061995 | A. Round House | 6 1 -100\r\n\n | OK |
| 223581 | dImak24 | astro_lion | A. Round House | 6 1 -6\r\n\n | WRONG_ANSWER |
| 223602 | dImak24 | Etrapanob | A. Round House | 6 1 -100\r\n\n | WRONG_ANSWER |
| 223673 | dImak24 | hk10july | A. Round House | 6 1 -100\r\n\n | WRONG_ANSWER |
| 223700 | dImak24 | I_love_CC | A. Round House | 6 1 -100\r\n\n | WRONG_ANSWER |
| 223769 | dImak24 | akjain | B. Qualifying Contest | 3 1\r\nA 1 800\r\nB 1 800\r\nC 1 100\r\n\n | WRONG_ANSWER |
| 223823 | dImak24 | Etrapanob | B. Qualifying Contest | 2 1\r\nA 1 800\r\nB 1 800\r\n\n | WRONG_ANSWER |
| 223858 | dImak24 | miss_invictus | B. Qualifying Contest | 2 1\r\nA 1 800\r\nB 1 800\r\n\n | WRONG_ANSWER |
| 223880 | dImak24 | ravichan | B. Qualifying Contest | 2 1\r\nA 1 800\r\nB 1 800\r\n\n | WRONG_ANSWER |
| 224258 | dImak24 | chernyavskiy.dmitriy | A. Round House | 7 1 -100\r\n\n | WRONG_ANSWER |
| 223203 | jerjerinmylefthand | Ann_Ulrikh | A. Round House | 10 5 -27\r\n\n | WRONG_ANSWER |
| 223209 | jerjerinmylefthand | tks | A. Round House | 10 5 -27\r\n\n | WRONG_ANSWER |
| 223210 | jerjerinmylefthand | kas0109 | A. Round House | 10 5 -27\r\n\n | WRONG_ANSWER |
| 223216 | jerjerinmylefthand | Aliir | A. Round House | 10 5 -27\r\n\n | WRONG_ANSWER |
| 223498 | jerjerinmylefthand | sharmaantra | A. Round House | 10 5 -27\r\n\n | WRONG_ANSWER |
| 223654 | jerjerinmylefthand | kas0109 | B. Qualifying Contest | 2 1\r\na 1 1\r\nb 1 1\r\n\n | WRONG_ANSWER |
| 223685 | jerjerinmylefthand | Aliir | B. Qualifying Contest | 3 1\r\na 1 4\r\nb 1 3\r\nc 1 3\r\n\n | WRONG_ANSWER |
| 223742 | jerjerinmylefthand | arpitbajaj95 | B. Qualifying Contest | 2 1\r\na 1 1\r\nb 1 1\r\n\n | OK |
| 223765 | jerjerinmylefthand | m.khooryani | B. Qualifying Contest | 2 1\r\na 1 1\r\nb 1 1\r\n\n | WRONG_ANSWER |
| 223770 | jerjerinmylefthand | arpitbajaj95 | B. Qualifying Contest | 3 1\r\na 1 4\r\nb 1 4\r\nc 1 3\r\n\n | WRONG_ANSWER |
| 223841 | jerjerinmylefthand | Z0RR0 | B. Qualifying Contest | 2 1\r\na 1 0\r\nb 1 0\r\n\n | WRONG_ANSWER |
| 223885 | jerjerinmylefthand | Ann_Ulrikh | B. Qualifying Contest | 3 1\r\na 1 2\r\nb 1 1\r\nc 1 1\r\n\n | WRONG_ANSWER |
| 224083 | jerjerinmylefthand | abhi04code | B. Qualifying Contest | 2 1\r\na 1 1\r\nb 1 1\r\n\n | WRONG_ANSWER |
| 224137 | jerjerinmylefthand | arpitbajaj95 | C. Tanya and Toys | 1 5\r\n10\r\n\n | OK |
| 224214 | jerjerinmylefthand | Lambo | C. Tanya and Toys | #include \r\nint main() {\r\nprintf("1... | Validator 'val.exe' returns exit code 3 [FAIL ... |
| 224220 | jerjerinmylefthand | Lambo | C. Tanya and Toys | *******************************\n*** The hack ... | Validator 'val.exe' returns exit code 3 [FAIL ... |
| 224245 | jerjerinmylefthand | Lambo | C. Tanya and Toys | *******************************\n*** The hack ... | RUNTIME_ERROR |
659A - Round House
As you can see the biggest problem was with large (bigger than n) and negative b. A lot of people forgot to use modulo properly (unfortunately in many languages, such as C++, -7 mod 10 is still -7, instead of 3, as in Python or just in many applications of math).
P.S. I love this hack: 224757. Take a look at solution first :]
659B - Qualifying Contest
Here pretests were quite weak, and many people for example answered "NO" if top two results are the same in each region (that is if top1.score == top2.score), which is obviously not true, because if top2.score is different than top3.score (of top3.score doesn't exist at all, the answer is simple). Other version of this bug was checking if top1.score == top2.score and top2.score == top3.score.
659C - Tanya and Toys
Most of the hacks for this problems are simply array bounds of memory limits (you cannot have an array of 109 elements), nothing too complicated.
Thanks for reading and liking, please comment your special hacks from this round. Also many thanks to Codeforces Team for wonderful API!
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