题解 | #LRU Cache#

import java.util.*;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        LinkedHashMap<Integer, Integer> lru = new LinkedHashMap<>();
        Integer n = Integer.valueOf(in.nextLine());
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            String line = in.nextLine();
            String[] strs = line.split(" ");
            if (strs[0].equals("p")) {
                Integer key = Integer.valueOf(strs[1]);
                Integer val = Integer.valueOf(strs[2]);
                lru.put(key, val);
                if (lru.size() > n) {
                    Iterator<Integer> it = lru.keySet().iterator();
                    Integer tmp = it.next();
                    lru.remove(tmp);
                }
            } else if (strs[0].equals("g")) {
                Integer key = Integer.valueOf(strs[1]);
                int val = -1;
                if (lru.containsKey(key)) {
                    val = lru.get(key);
                    lru.remove(key);
                    lru.put(key, val);
                }
                System.out.println(val);
            }
        }
    }
}