这个输入输出是啥意思，是ACM模式要把["LFUCache","put","put","get","put","get","get","put","get","get","get"]这种命令解析成具体操作吗？直接写道main里行不行？ LFU cache = new LFU(2);
cache.put(1, 1);
cache.put(2, 2);
System.out.println(cache.get(1)); // 返回 1
cache.put(3, 3); // 去除 key 2
System.out.println(cache.get(2)); // 返回 -1 (未找到)
System.out.println(cache.get(3)); // 返回 3
cache.put(4, 4); // 去除 key 1
System.out.println(cache.get(1)); // 返回 -1 (未找到)
System.out.println(cache.get(3)); // 返回 3
System.out.println(cache.get(4)); // 返回 4
