题解 | #配置文件恢复#

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);
        // 注意 hasNext 和 hasNextLine 的区别
        Map<String, String> cmd1 = new HashMap<>();
        Map<String, String> cmd2 = new HashMap<>();
        cmd1.put("reset", "reset what");

        cmd2.put("reset board", "board fault");
        cmd2.put("board add", "where to add");
        cmd2.put("board delete", "no board at all");
        cmd2.put("reboot backplane", "impossible");
        cmd2.put("backplane abort", "install first");
        String errMsg = "unknown command";

        while (in.hasNextLine()) {
            String a = in.nextLine();
            // 暴力解只有一串
            if (a.split(" ").length == 1 && a.length() <= "reset".length()) {
                boolean flag = true;
                for (int i = 0; i < a.length(); i++) {
                    if (a.charAt(i) != "reset".charAt(i)) {
                        flag = false;
                        break;
                    }
                }
                System.out.println(flag ? cmd1.get("reset") : errMsg);
            } else if (a.split(" ").length == 2) {
                // 暴力解有且只有二串，遍历两串是否相符，比较耗时
                String[] arr = a.split(" ");
                Iterator<String> iter = cmd2.keySet().iterator();
                int count = 0;
                String key = "";
                while (iter.hasNext()) {
                    String nextKey = iter.next();
                    String[] nextKeyArr = nextKey.split(" ");
                    boolean flag1 = true;
                    if (!nextKeyArr[0].startsWith(arr[0])) {
                        flag1 = false;
                    }
                    if (flag1) {
                        boolean flag2 = true;
                        if (!nextKeyArr[1].startsWith(arr[1])) {
                            flag2 = false;
                        }
                        if (flag2) {
                            count++;
                            key = nextKey;
                        }
                    }
                }
                System.out.println(count == 1 ? cmd2.get(key) : errMsg);
            } else {
                System.out.println(errMsg);
            }
        }
    }
}