I would like to address the similarity noticed in my solution.
Think of the array as a sequence of numbers from 1 to n, and you are interested in picking a continuous segment (subarray). For any chosen segment, you compute the XOR of all its elements.
Now, instead of directly checking every segment, notice this:
The XOR of a segment from l to r can be represented using prefix XOR values. So the problem essentially becomes: how many pairs of positions define a segment whose XOR evaluates to 0?
Another way to see it:
Imagine building an array where each position stores the XOR of all elements from the start up to that index. If two positions have the same prefix XOR value, then the segment between them has XOR = 0. So instead of focusing on segments, you’re really counting pairs of indices with equal prefix XOR values.
Now add the twist:
The sequence [1..n] has a very structured behavior — its prefix XOR doesn’t change randomly, it follows a repeating cycle depending on the index modulo 4. Because of this, you don’t have many distinct XOR values to deal with—just a few repeating patterns.
So the problem shifts from:
“Check all subarrays”
to:
“Group indices based on their prefix XOR pattern and count how many valid pairs can be formed.”
And if there’s a special index x involved:
You split the array into two parts (before x and after x), Count how many indices in each part fall into each XOR group, Then combine those counts to get the final answer.
This approach is a natural consequence of the mathematical properties of the sequence and matches the general idea described in the editorial. As a result, independently derived solutions are likely to look very similar in logic and structure.
I wrote my code independently during the contest without consulting any external material.
Hence, any resemblance is due to the inherent nature of the problem rather than any form of collaboration.
Submission: https://mirror.codeforces.com/contest/2225/submission/372032850
I kindly request the Codeforces team to recheck my submission and review all my submissions in this contest. If possible, please reconsider the skipped/flagged status after verification.
I fully respect the platform’s rules and would appreciate a fair review.
