The approximation ratio of the greedy algorithm for the metric traveling salesman problem

We prove that the approximation ratio of the greedy algorithm for the metric Traveling Salesman Problem is ? ( log n ) . Moreover, we prove that the same result also holds for graphic, euclidean, and rectilinear instances of the Traveling Salesman Problem. Finally we show that the approximation ratio of the Clarke-Wright savings heuristic for the metric Traveling Salesman Problem is ? ( log n ) .