Dynamic Programming solution to the TSP

This function solves the Traveling Salesman Problem (TSP) using Dynamic programming (DP).

The function is based on the paper by Held and Karp from 1962. The DP is guaranteed to provide the accurate (optimal) result to the TSP, but the time complexity of this algorithm is O(2^n n^2), which limits the use of this algorithm to 15 cities or less.

NOTE: For reasonable runtime, please do not try to calculate a tour of more than 13 cities. DP is not for large sets of cities.