In this paper, we propose an efficient heuristic for the Virtual Network Function (VNF) reconfiguration problem in the context of 5G network slicing. This problem consists in reallocating the VNFs to fit the network changes, by transforming the current state of deployed services, e.g., the current placement of Virtual Machines (VM) that host VNFs, to another state that updates providers’ objectives. We rely on the topological sorting algorithm and the Feedback Arc Set (FAS) problem to build our heuristic which is an alternative of an Integer Linear Programming (ILP) solution that we have already proposed in [1]. Experimental results show that our heuristic solves the problem in a few seconds even for large network infrastructures.