Hi, I'm having trouble solving this problem. I was thinking of applying a Markov sequence property ( The average length of the cycle path of a node is the inverse of the probability of being in this node ), so the problem is reduced to an equation system. However, it's a 10⁵ x 10⁵ sparse matrix (at most 10⁵ non-zero elements). I don't know if there is a gaussian elimination method for this kind of matrix or if the approach is incorrect. Thanks.