Leetcode 517. Super Washing Machines

Given an array of dress counts where in each move any subset of machines can simultaneously pass one dress from each selected machine to one adjacent neighbor, compute the minimum number of such parallel moves required to make all machines hold the same number of dresses (or return -1 if impossible). The core challenge is checking feasibility (total must be divisible by n) and reasoning about cumulative imbalances/local transfer requirements to derive the minimum rounds.