8.贪婪算法

# 最少的电台数，覆盖最多的州
# 需要覆盖的州的集合
states_needed = set(["mt", "wa", "or", "id", "nv", "ut", "ca", "az"])

# 各电台覆盖的州的集合
stations = {}
stations["kone"] = set(["id", "nv", "ut"])
stations["ktwo"] = set(["wa", "id", "mt"])
stations["kthree"] = set(["or", "nv", "ca"])
stations["kfour"] = set(["nv", "ut"])
stations["kfive"] = set(["ca", "az"])

# 最终电台集合
final_stations = set()

# 每次循环，选出能覆盖最多未选中的州的电台
while states_needed:
    best_station = None
    # 已经覆盖的州集合，初始化
    states_covered = set()
    for station, states in stations.items():
        covered = states_needed & states
        if len(covered) > len(states_covered):
            best_station = station
            states_covered = covered

    states_needed -= states_covered
    final_stations.add(best_station)

print(final_stations)