题解 | #MP3光标位置#

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);

        while (in.hasNext()){
            String total = in.nextLine();
            String ops = in.nextLine();

            solution(Integer.parseInt(total), ops);
        }
    }

    /**
     * 模拟法
     * @param total
     * @param ops
     */
    private static void solution(int total, String ops){

        // 光标当前位置
        int currIndex = 1;
        // 当前页第一位置
        int firstIndex = 1;

        // 歌曲总数<=4
        if(total <= 4){
            for(char op: ops.toCharArray()){
                if(op == 'U'){
                    if(currIndex == 1){
                        currIndex = total;
                    }else{
                        currIndex--;
                    }
                }else if(op == 'D'){
                    if(currIndex == total){
                        currIndex = 1;
                    }else{
                        currIndex++;
                    }
                }
            }

            for(int i=1; i<=total; i++){
                System.out.print(i+" ");
            }
        }
        // 歌曲总数大于4
        else{
            for(char op: ops.toCharArray()){
                if(op == 'U'){
                    // 光标在第一首歌曲上
                    if(currIndex == 1){
                        currIndex = total;
                        firstIndex = total-3;
                    }else{
                        if(currIndex == firstIndex){
                            currIndex--;
                            firstIndex--;
                        }else{
                            currIndex--;
                        }
                    }
                }else if(op == 'D'){
                    // 光标在最后一首歌上
                    if(currIndex == total){
                        currIndex = 1;
                        firstIndex = 1;
                    }else{
                        if(currIndex-firstIndex==3 && firstIndex < total-3){
                            currIndex++;
                            firstIndex++;
                        }else{
                            currIndex++;
                        }
                    }
                }
            }

            for(int i=firstIndex; i<=Math.min(firstIndex+3, total); i++){
                System.out.print(i+" ");
            }
        }
        System.out.println();
        System.out.println(currIndex);
    }
}