[Official] July Cook-Off 2020 - Post-contest discussion - Live stream session

Hey all,

We plan to have an informal live stream for discussing the problems of July Cook-Off 2020.

The details are as follows:

  • Agenda:
    Discussion of COOK120 problems.
    The problems will be discussed in increasing order of difficulty.

  • Session Panelist:
    Rajarshi Basu

  • Date-Time:
    20th July 2020.
    6pm to 8pm IST

  • To register:
    If you are interested just register by clicking on the “Going” button below the title of this post at the top.

Note: Entry to the Zoom session will be on first come first serve basis - limited to 100 seats.

If there are any specific queries that you have from these problems, please post them below after the contest, and we will try to answer them during the session.

[Update 1]
Zoom Meeting Details -
Topic: [Official] July Cook-Off 2020 - Post-contest discussion - Live stream session
Time: Jul 20, 2020 06:00 PM India

Join Zoom Meeting

Meeting ID: 851 2857 5278
Password: 932771

[Update 2]
Catch us live on YouTube here -


How will we get the zoom link on 20 july ?

In the question Even-tual reduction :

  • I quickly figured out that the input string must have all characters even number of times,
    so I xor’d all the characters in input string, as in the following code, but the result was wrong answer, so I ended up using hashing.
		int x=0;
		for(int i=0;i<n;i++){
			x= x^(s[i]-'a'+1);
			cout << "YES";
			cout << "NO";

could you explain what is going wrong here?
It passed the test-cases given in the question.

Meeting ID: 851 2857 5278
Password: 932771

same issue facing.

My submission for OR-thodox Distinction during the contest got Correct Answer Verdict. However, it’s clearly an incorrect solution. For the test case below:
7 2 1
my code will give output “YES” while the correct output is “NO”. It’s simply the first array in reversed order from the given test cases of the problem.

Link to my solution below:

Actually I checked if the suffix OR is same for any two consecutive elements, but the same needs to be done from the front, i.e. for the prefix.

For your code answer to array
having character index values [1,4,5] is zero, but they are all different.