if someone in the comment section can provide exact implementation code and explanation to the above all 8 different problems then it would be very helpful.

I will reach CM. Challenge accepted.

will it be unrated ?

Hey thankyou, I just corrected my mistake.

Hey thankyou i just mistakenly write the sums...

I am facing a lot difficulty in understanding problem D.

can someone explain it to me.

there are a lot of different rules out there the one you need here is that: if the alternating sum and difference of 3 digits from left to right is divisible by 7 then the number will be divisible by 7 for example: 12,332,455 :- value = (455)-(332)+(12) = 135 ; which is not divisible by 7 hence number is not divisible by 7.

for n!>=6 (i.e. n>=3, n!=6*k) number of digits will be multiple of 3 and 2, hence you always have even pair of alternating sum of 3 digits hence above value will always be 0 hence divisible by 7.

https://mirror.codeforces.com/contest/2043/submission/298352521

Hey someone please take a look at my submission and tell me the mistake, I am using max and min subarray sum ending at a index to find the answer.

Ok if you want to understand Problem E...

watch this super easy code.... https://mirror.codeforces.com/contest/2051/submission/298088585

What i did was to use sweep line algorithm to find efficiently the number of negative reviews for a given price (which will be someone among a's or b's) and uses binary search to find the customers who can afford the tree and if negative reviews are below the constraint(k) booommm we got a possible answer and i update my final answer.

Third.

I will quit competitive programming...

I don't know a lot of math but still i can say that:

i goes from : (n-1)--->0; j goes from : (i)---->0;

overall the inner statements of second loop will run like :(n-1)+(n-2)+(n-3)+..+3+2+1 times.

hence O(n^2).

Is it only me who find it really difficult to understand Problem D tutorial?

I think it is O(N^2) ?

Yeah..

I have a doubt in problem C, if the problem does not say that string starts with '1' does it will change the answer?

I yes how?

Can't we include visual explanation with images in editorial? then many more participants can upsolve the problems and can Improve, i usually find difficulty to understand the text solution.

Proof (for problem C) of why (1,n) is always one of the substring.

let leftmost '1' occurs at pth position(from right to left) no other substring can have (p+1)th position '1' hence can never exceed the xor of one pair created using (1,n) as one substring.

also 2^k> 2^(k-1)+ 2^(k-2)....... +2+1. so if you could get xor with all bits '1' and with length (p-1) it will still be smaller than which could be generated using (1,n) (pth position '1').

please correct me if i am wrong.

what is k here in problem C ?

how do i will know how many rooks needs to be painted ?

can you write one for me ,please.

Do we need to use dp or not ?? Are you presenting some greedy solution ?

in second how to prove this that if we can not separate array into two segments then it is also not possible for us to do it if the number of segments are increased ?