### flamestorm's blog

By flamestorm, 22 months ago,

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1742A - Sum

Idea: flamestorm

Tutorial
Solution

1742B - Increasing

Idea: mesanu

Tutorial
Solution

1742C - Stripes

Idea: flamestorm

Tutorial
Bonus
Solution

1742D - Coprime

Tutorial
Solution

1742E - Scuza

Idea: mesanu

Tutorial
Solution

1742F - Smaller

Idea: SlavicG

Tutorial
Solution

1742G - Orray

Idea: SlavicG

Tutorial
Solution
• +58

| Write comment?
 » 22 months ago, # |   +7 B was just a few lines with the help of STL :D (Submission: 176051852)
•  » » 22 months ago, # ^ |   0 Nice!
•  » » 22 months ago, # ^ | ← Rev. 2 →   0 Or int n; cin >> n; vector a(n); for(auto &x : a) cin >> x; cout << (set(a.begin(), a.end()).size()==a.size()?"YES":"NO") << '\n'; which I find even simpler.
•  » » 12 months ago, # ^ | ← Rev. 2 →   0 I know your solution is correct but here he elaborates to us the idea of the problem not just the solution. great respect
 » 22 months ago, # | ← Rev. 2 →   0 Problem C,When I judge the horizontal and vertical directions of a color,my submission-->175928516, I can't pass the test. But when I only judge the corresponding direction of a color, it passed,my submission-->176020169 Can someone tell me why
•  » » 22 months ago, # ^ |   0 Look at the title,some horizontal rows have been painted red, and some vertical columns have been painted blue.
•  » » » 22 months ago, # ^ |   +1 I also didn't read it properly costed me more than an hour to cause it took more than 15 mins to run on pretests :'(
•  » » 22 months ago, # ^ |   +9 Consider this caseBBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB RRRRRRRRAnswer : 'R' Output : 'B'
 » 22 months ago, # |   +13 for problem C, many of us missed this case :( BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB BBBBBBBB RRRRRRRRAnswer : 'R' Output : 'B'
•  » » 22 months ago, # ^ |   0 I think the answer should be R, as it has the occurrence 8 consecutive times in a row. Please tell, why are there so many messages related to this?????
•  » » » 22 months ago, # ^ | ← Rev. 2 →   0 Because many of us just checked whether the entire row is same color rather than checking entire row is Red Or Not. This also follow for column also.
 » 22 months ago, # |   0 why is my 176088793 getting WA on 11 (problem D)
•  » » 22 months ago, # ^ |   0 when the input array is 2 6 10 15 your output is 0 because when you reach 6 the gcd will be 1 but actually there is no coprime number between 6 , 10 , 15 but it is true that their gcd is 1 The correct output should be 5 by taking 2 and 15
 » 22 months ago, # |   0 I got TLE in problem E. My submission is 176039360 . How can I improve this?
•  » » 22 months ago, # ^ |   +3 As per your solution I suggest you to have a read on Time Complexity Analysis It would be helpful for you to understand why your code is getting TLE
 » 22 months ago, # |   0 I got TLE on Problem D. Not sure why. How can I improve this solution
•  » » 22 months ago, # ^ |   0 Instead of keeping track of every index , you can consider the values of the array elements , that can go up to only 10^3 . Now , if you run two for loops , then time taken O(10^3*10^3) and for T=10 test cases , O(10*10^3*10^3) = O(10^7) [neglecting time complexity for __gcd(a,b) stl ].
 » 22 months ago, # |   +5 Video Editorial for Chinese：Bilibili
•  » » 22 months ago, # ^ |   0 Is that Chinese youtube?
•  » » » 22 months ago, # ^ |   0 YES，and better than YouTube
 » 22 months ago, # |   +6 I think there is an easier way to implement the algorithm in G's tutorial. 176054281
 » 22 months ago, # |   +4 Weak pretest in problem F.
 » 22 months ago, # | ← Rev. 4 →   0 I am getting the Wrong answer for F on test case 2 .. my submission- hereplz someone help me out ::) I got my mistake
 » 22 months ago, # |   0 sadly, i misread the "OR" as "XOR" and failed to ak
•  » » 22 months ago, # ^ |   0 oh bad luck
•  » » » 22 months ago, # ^ |   0 it's more like oh bad concentration
 » 22 months ago, # | ← Rev. 2 →   0 flamestorm is the solution of bonus of problem C like this :we go through each row except the ones with full red then check whether if a column is painted blue whether it is painted red in any of the previous rows and if a column is painted red whether it is painted blue in any of the previous rows and if a column is white whether it is painted blue in any of the previous rows; If any of these three happens then input grid is invalid otherwise validIs it correct ?
 » 22 months ago, # | ← Rev. 2 →   0 Hey flamestorm,In problem C, the valid input must contain exactly one of theses situations:1- Have one or more rows full of R's2- Have one or more columns full of B'sotherwise, the input is invalid Is it correct ?
•  » » 22 months ago, # ^ | ← Rev. 2 →   -6 Well, those are a part of the conditions, but there seems to be more invalid cases to consider. The following is one example. .B.BB... .B.BB... .B.BB... RBRRBRRR RBRBRRRR .B.BB... .B.BB... .B.BB... 
•  » » » 22 months ago, # ^ |   +1 I don't see any reason of downvoting him , he made a correct point.Maybe he has bad record in past in terms of commenting & posting but that doesn't have any relation with this,And why am I saying this? I am saying this because we all make mistakes in life ,doesn't mean we can't move forward
 » 22 months ago, # |   0 I got TLE in F question for Test Case #2, any ideas/hints how can I improve the code? submission
•  » » 22 months ago, # ^ |   0 You need to save the count of every character, as k can be 10^5 every time and there are 10^5 queries the size of the string can exceed 10^10. You can check out my submission : https://codeforces.com/contest/1742/submission/175994173
 » 22 months ago, # |   +4 In problem D I have gotten wrong answer on test 24 on an invalid test int the statement they said that n must be greater than 2 but I have had wrong answer on a test with n=1 so please rejudge the problem SlavicG , mesanu , flamestorm please do something 175973439 .
•  » » 22 months ago, # ^ |   0 Help him pleez
•  » » 22 months ago, # ^ |   +1 Help him, he deserves achieving pupil :(
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22 months ago, # ^ |
+1

Agree

# Help_Rida

•  » » 22 months ago, # ^ |   +1 that is not fair, please help him .
•  » » 22 months ago, # ^ |   +1 it is unfair not to rejudge his submission
•  » » » 22 months ago, # ^ | ← Rev. 2 →   0 totaly agreeeehiz frendz need mental aid
 » 22 months ago, # |   0 In $C$, why didn't they put $n$ and $m$ $(1$ $\le$ $n,m$ $\le$ $1000)$ or something like that?I think when $n=m=8$ problem is more like Div.4 $B$ problem, this could make problem $C$ little harder, just as hard as a Div.4 $C$ should be.
•  » » 22 months ago, # ^ |   0 I don't think constraints matter at all in C ,n,m<=1000 doesn't make any difference in solution
•  » » » 22 months ago, # ^ |   0 In some solutions it actually does matter.Example: 175929785 from ltunjic
•  » » » » 22 months ago, # ^ |   0 how does it matter? you can just create RRRRR....RRRR string just by appending R m times
•  » » » » » 22 months ago, # ^ |   0 Right, but I still think problem would be little harder for beginners.
 » 22 months ago, # |   0 In Problem B, the checker log is telling me that I gave a wrong answer in test case #2 while my answer is the same as the output. As you can see in the submission, the 25th token is correct. Am I missing something? 176210112
•  » » 22 months ago, # ^ |   -8 Your code is dereferencing the value of $a[n]$. This is undefined behaviour, and may have caused a WA any moment.
 » 22 months ago, # |   0 Have a problem with G176665365but the test is really huge and I can catch the problem/Maybe someone has the idea?
•  » » 7 weeks ago, # ^ |   0 Buddy just ChatGPTed and asked us to rectify it lmao
 » 19 months ago, # | ← Rev. 2 →   0 I guess I didn't understand F correctly...The is the 10th test: 1 5 2 1 bb 1 2 b 2 3 b 1 2 c 2 3 bcdbweakpretests Official answer is:YESYESYESYESYES.Why it isn't:YESNOYESNOYES?UPD: solved it
 » 12 months ago, # |   0 In problem 1742D, I am getting my 1st test(5th array) wrong which is 31 instead of 10, also i don't know why 10 is the answer for the fifth array, as 15 and 16 are coprime also.
•  » » 12 months ago, # ^ |   0 https://gist.github.com/ryze-7/285ff124c4e164a62e9e945e5a1d1310 link for my code
 » 5 months ago, # | ← Rev. 2 →   0 251250861 whats wrong with my code it gives the correct output in the editor
 » 3 months ago, # |   0 For Solution DWe just have to store the value of index to the key of the vector as the for loop is progressing it generally stores the largest index value.for(int i = 1; i <= n; ++i) { int x; cin >> x; id[x].push_back(i); // we can actually store id[x]=i+1; }