Round of the big guys,

Hope to be on that league some day :)

Last time I was defeated by the output-only task.

Hope I can perform well in this AGC.

Rafi22 will trash his opponents orz

After years, finally first rated AGC for me (except when I was spec). Hope to solve $$$\epsilon \gt 0$$$ problems.

My stupid brain thought C was bridge lol, thought I proved it..

In Problem A, consider an initial sequence $$$A$$$ and a final sequence $$$C$$$, where each element $$$C[i]$$$ is derived from $$$A[i]$$$. I observed that each $$$C[i]$$$ can be expressed as the XOR of a contiguous subsequence of $$$A$$$, specifically:

where $$$l \leq i \leq r$$$, and $$$\oplus$$$ denotes the bitwise XOR operation.

To represent this relationship, I defined a binary matrix $$$M$$$ such that:

Notably, at least two elements contribute to each XOR expression, and $$$A[i]$$$ always contributes to the expression for $$$C[i]$$$.

I'm wondering if it is possible to characterize this matrix M (i.e. what is it's structure , what constraints or properties it satisfies) and use that to find the final answer. Did anyone who solved problem A try this way ?

A, B and C are nice problems. Enjoyed them.

In the editorial of the problem A said "When an even-length sequence is split into two parts of odd + odd length or odd + even length". What were meant by odd + even ? Should it be there at all ?

Such a good round.

A question on Task C.

If for every vertex $$$i$$$ we record the edges to every components after we delete $$$i$$$ as $$${c'}_i$$$.

Is $$$c'$$$ same with $$$c$$$?