|As exploiting Unmanned Aerial Vehicles (UAVs) as mobile elements is a new research trend recently, approximation algorithms to solve path planning problems for UAVs are promising approaches. In this paper, we divide problems in two main objectives, cost and reward. We introduce some representative approximation algorithms, which focus on maximizing reward or minimizing travel time. Particularly, we explore path planning for each node visit within different time deadline. In recent works, researchers extend classic algorithms to distributed path planning algorithms for multiple UAVs.