题解 | #MP3光标位置#

#include <iostream>
#include <list>
using namespace std;
int main()
{
    int n;
    string cmd;
    while (cin >> n >> cmd)
    {
        int index = 1, top = 1;
        for(auto i:cmd)
        {
            if(i=='D')
            {
                index++;
                if(index>n)index = top = 1;//回到第一首
                else if(index>top+3)top++;//下滑
            }
            else
            {
                index--;
                if(index==0){index = n;top = max(n-3,1);}//到最后一首
                else if(index<top)top--;//上滑
            }
        }
        for(int i=0;i<4;i++)if(top+i<=n)cout<<top+i<<" ";
        cout << endl << index << endl;
    }
}