https://www.codechef.com/problems/QRYLAND This is a problem of heavy light decomposition but I was unable to get about the hash function(xor) concept which is being used in the editorial(https://discuss.codechef.com/t/qryland-editorial/29306) in order to verify that whether the path from u to v of length l is a permutation of numbers from 1 to l or not so if someone could tell something about the concept or the idea then it would be great.