(Traveling salesperson problem) The traveling salesperson problem (TSP) is to find a shortest round-trip route that visits each city exactly once and then returns to the starting city

(Traveling salesperson problem) The traveling salesperson problem (TSP) is to find a shortest round-trip route that visits each city exactly once and then returns to the starting city. The problem is equivalent to finding a shortest Hamiltonian cycle in Programming Exercise 28.17. Add the following method in the WeightedGraph class:

// Return a shortest cycle
// Return null if no such cycle exists
public List<Integer> getShortestHamiltonianCycle()