旅行商问题： 某售货员要到若干城市去推销商品，已知各城市之间的路程（或旅费）。他要选定一条从驻地出发，经过每个城市一遍，最后回到驻地的路线，使总的路程（或旅费）最小。-traveling salesman problem : A salesman to a number of cities to sell commodities, known the distance between cities (or travel). He s