Algorithm for finding the best “route” of tasks
If you have just one person to complete the tasks, this is the (in)famous Travelling Salesman Problem (TSP), which is NP-complete, so an efficient exact algorithm is a very remote possibility. Unless your problem is quite small, you'd have to settle for approximate solutions. There are algorithms that can solve enormous instances of TSP in (somewhat) reasonable time, but I have no pointers at hand.