The Traveling Salesman Problem (TSP) is a classic optimization challenge that seeks the shortest possible route for a salesman to visit each city in a list exactly once and return to the origin city.
For this problem, you task is to find a constructive heuristic function `select_next_node` that can generate next node to visit for the salesman.
Your goal is to minimize the objective, which is the average test tour distances for the salesman (called "score" or "objective" of solution).