题解 | #MP3光标位置#

分情况讨论

好怀念初中时候用的mp3

#include <iostream>
#include <bits/stdc++.h>
#include <vector>
using namespace std;
const int N = 4;
void do_work_under4(int n,string str);
void do_work_above4(int n,string str);
int main() {
    int n;
    string str;
    while(cin>>n>>str){
        if(n<=4){
            do_work_under4(n,str);
        }
        else{
            do_work_above4(n,str);
        }
    }
    
}
void do_work_under4(int n,string str){
    vector<int>page;
    for(int i = 0;i<n;i++){
        page.push_back(i+1);
    }
    int index = 0;
    for(auto &ch:str){
        if(ch=='U'){
            if(index==0) index=page.size()-1;
            else  index = index-1;
        }
        else{
            if(index==page.size()-1) index = 0;
            else index = index+1;
        }
    }
    for(int &ch:page){
        cout<<ch<<" ";
    }
    cout<<endl;
    cout<<page[index]<<endl;
}
void do_work_above4(int n,string str){
    vector<int>page = {1,2,3,4};
    int last = 3;
    int index = 0;
    for(auto &ch:str){
        if(ch=='U'){
            if(index==0&&page[0]==1){
                index = last;
                page = vector<int>({n-3,n-2,n-1,n});
            }else if(index==0&&page[0]!=1){
                for(int &ch:page){
                    ch--;
                }
            }else{
                //index!=0
                index--;
            }
        }
        else if(ch=='D'){
            if(index==last&&page[index]==n){
                index = 0;
                page = vector<int>({1,2,3,4});
            }else if(index==last&&page[index]!=n){
                for(int &ch:page){
                    ch++;
                }
            }else{
                //index!=last
                index++;
            }
        }
    }
    for(int &ch:page){
        cout<<ch<<" ";
    }
    cout<<endl;
    cout<<page[index]<<endl;
}
// 64 位输出请用 printf("%lld")