题解 | #MP3光标位置#

import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);
        int numsOfSongs = scan.nextInt();
        int[] arr = new int[numsOfSongs];
        for (int i = 0; i < numsOfSongs; i++) {
            arr[i] = i + 1;
        }
        String order = scan.next();
        char[] Order = order.toCharArray();
        int cur = 0;//表示当前所在位置的数组下标
        if (numsOfSongs <= 4) {
            for (int i = 0; i < Order.length; i++) {
                if (Order[i] == 'D') {
                    if (cur == numsOfSongs - 1) {
                        cur = 0;
                    } else {
                        cur++;
                    }
                } else {
                    if (cur == 0) {
                        cur = numsOfSongs - 1;
                    } else {
                        cur--;
                    }
                }
            }
            for (int i = 0; i < numsOfSongs; i++) {
                System.out.print(arr[i] + " ");
            }
            System.out.println();
        } else {
            int top = 0;//表示开始的时候屏幕顶部的位置的下标
            int bottom = 3;//表示开始的时候屏幕底部的位置的下标
            //由top和bottom维护一个窗口，大小始终是4
            for (int i = 0; i < Order.length; i++) {
                if (Order[i] == 'D') {
                    if (cur < bottom) {
                        cur++;
                    } else {
                        //此时就是cur == bottom
                        //cur并不会大于bottom,因为这个创就是我们自己维护边界的，cur只能在窗口内部活动
                        if (bottom < numsOfSongs - 1) {
                            bottom++;
                            cur++;
                            top++;
                        } else {
                            //此时就是bottom == numsOfSongs - 1,即来到了底部
                            cur = 0;
                            top = 0;
                            bottom = 3;
                        }
                    }
                } else { //指令不是'D'就是'U'
                    if (cur > top) {
                        cur--;
                    } else { //此时就是cur == top
                        if (top > 0) {
                            top--;
                            bottom--;
                            cur--;
                        } else { //否则就是top == 0了
                            top = numsOfSongs - 1 - 3;
                            bottom = numsOfSongs - 1;
                            cur = bottom;
                        }
                    }
                }
            }
            for (int i = top; i <= bottom; i++) {
                System.out.print(arr[i] + " ");
            }
            System.out.println();
        }
        System.out.println(cur + 1);

    }
}