Python:TSP-最近的城市

我必须用启发式算法解决TSP问题，我发现了这一点：我创建了自己的变体：推销员现在去最近的城市。。。但是，这种重复性并不奏效。在某些情况下，推销员只在两个城市之间走，而我有无限循环。请帮忙

routes = []

def find_paths_closest(node, cities, path, distance):
    path.append(node)

    if len(path) > 1:
        distance += cities[path[-2]][node]

    # If path contains all cities and is not a dead end,
    # add path from last to first city and return.
    if (len(cities) == len(path)) and (cities[path[-1]].has_key(path[0])):
        global routes
        path.append(path[0])
        distance += cities[path[-2]][path[0]]
        print path, distance
        routes.append([distance, path])
        return

    minimum = 0
    for i in range(1, len(cities[node])):
        if cities[node].keys()[i] not in path:
            if cities[node].values()[minimum] > cities[node].values()[i]:
                minimum = i

    newnode = cities[node].keys()[minimum]

    find_paths_closest(newnode, dict(cities), list(path), distance)


def find_paths_brute_force(node, cities, path, distance):
    # Add way point
    path.append(node)

    # Calculate path length from current to last node
    if len(path) > 1:
        distance += cities[path[-2]][node]

    # If path contains all cities and is not a dead end,
    # add path from last to first city and return.
    if (len(cities) == len(path)) and (cities[path[-1]].has_key(path[0])):
        global routes
        path.append(path[0])
        distance += cities[path[-2]][path[0]]
        print path, distance
        routes.append([distance, path])
        return

    # Fork paths for all possible cities not yet used
    for city in cities:
        if (city not in path) and (cities[city].has_key(node)):
            find_paths_brute_force(city, dict(cities), list(path), distance)


if __name__ == '__main__':
    cities = {
        'RV': {'S': 195, 'UL': 102, 'M': 178, 'BA': 180, 'Z': 91},
        'UL': {'RV': 86, 'S': 107, 'N': 171, 'M': 123},
        'M': {'RV': 178, 'UL': 123, 'N': 170},
        'S': {'RV': 195, 'UL': 107, 'N': 210, 'F': 210, 'MA': 135, 'KA': 64},
        'N': {'S': 210, 'UL': 171, 'M': 170, 'MA': 230, 'F': 230},
        'F': {'N': 230, 'S': 210, 'MA': 85},
        'MA': {'F': 85, 'N': 230, 'S': 135, 'KA': 67},
        'KA': {'MA': 67, 'S': 64, 'BA': 191},
        'BA': {'KA': 191, 'RV': 180, 'Z': 85, 'BE': 91},
        'BE': {'BA': 91, 'Z': 120},
        'Z': {'BA': 120, 'BE': 85, 'RV': 81}
    }

    print "Start: RAVENSBURG"
    find_paths_brute_force('RV', cities, [], 0)
    print "\n"
    routes.sort()
    print "Shortest route: %s" % routes[0]

---

一旦你去过那里，你不应该从城市列表中删除这个城市吗？那个么你们就不能有一个循环，我不能，因为我指的是第一个if语句中的full cities数组。