①直接求解,字典序输出答案
HDU 1814 Peaceful Commission http://blog.youkuaiyun.com/a634771197/article/details/38585663
②二分枚举答案,判有无解
HDU 1815 Building roads http://blog.youkuaiyun.com/a634771197/article/details/38585903
HDU 1816 Get Luffy Out * http://blog.youkuaiyun.com/a634771197/article/details/38586361