[BOJ] 9019 DSLR (JAVA)

https://www.acmicpc.net/problem/9019

9019번: DSLR

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.LinkedList;
import java.util.Queue;
import java.util.StringTokenizer;

public class Main {
	
    public static void main(String[] args) throws Exception {

        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        StringBuilder sb = new StringBuilder();
        int T = Integer.parseInt(br.readLine());
        for (int tc = 0; tc < T; tc++) {
            StringTokenizer st = new StringTokenizer(br.readLine(), " ");
            int start = Integer.parseInt(st.nextToken());
            int end = Integer.parseInt(st.nextToken());
            boolean[] visited = new boolean[10000];
            Queue<Info> q = new LinkedList<>();
            visited[start] = true;
            q.offer(new Info(start, ""));

            while (!q.isEmpty()) {
                Info i = q.poll();

                if (i.num == end) {
                    sb.append(i.s).append("\n");
                    break;
                }

                int next = left(i.num);
                if (!visited[next]) {
                    q.offer(new Info(next, i.s + "L"));
                    visited[next] = true;
                }

                next = right(i.num);
                if (!visited[next]) {
                    q.offer(new Info(next, i.s + "R"));
                    visited[next] = true;
                }

                next = mul(i.num);
                if (!visited[next]) {
                    q.offer(new Info(next, i.s + "D"));
                    visited[next] = true;
                }

                next = minus(i.num);
                if (!visited[next]) {
                    q.offer(new Info(next, i.s + "S"));
                    visited[next] = true;
                }
            }
        }

        System.out.print(sb);

    }

    static int left(int num) {
        int next = num * 10;
        return next / 10000 + next % 10000;
    }

    static int right(int num) {
        return (num % 10) * 1000 + num / 10;
    }

    static int mul (int num) {
        return (num * 2) % 10000;
    }

    static int minus (int num) {
        return num == 0 ? 9999 : num - 1;
    }

    static class Info {
        int num;
        String s;

        Info (int num, String s) {
            this.num = num;
            this.s = s;
        }
    }
	
}