Submission #1014111

#	Time	Username	Problem	Language	Result	Execution time	Memory
1014111		Aiperiii	Building 4 (JOI20_building4)	C++14	100 / 100	169 ms	68936 KiB

building4

#include <bits/stdc++.h>
#define int long long
#define all(x) x.begin(),x.end()
#define ff first
#define ss second
#define pb push_back
using namespace std;
const int N=5e5+5;
pair <int,int> dp[N*2][2];
signed main(){
   ios_base::sync_with_stdio(0);
   cin.tie(0);cout.tie(0);
    int n;
    cin>>n;
    vector <int> a(n*2+1),b(n*2+1);
    for(int i=1;i<=n*2;i++){
        cin>>a[i];
    }
    for(int i=1;i<=n*2;i++){
        cin>>b[i];
    }
    dp[1][0]={0,0};
    dp[1][1]={1,1};
    for(int i=2;i<=n*2;i++){
        dp[i][0]={1e9,-1e9};
        dp[i][1]={1e9,-1e9};
    }
    for(int i=2;i<=n*2;i++){
        if(a[i]>=a[i-1]){
            dp[i][0].ff=min(dp[i][0].ff,dp[i-1][0].ff);
            dp[i][0].ss=max(dp[i][0].ss,dp[i-1][0].ss);
        }
        if(a[i]>=b[i-1]){
            dp[i][0].ff=min(dp[i][0].ff,dp[i-1][1].ff);
            dp[i][0].ss=max(dp[i][0].ss,dp[i-1][1].ss);
        }
        if(b[i]>=b[i-1]){
            dp[i][1].ff=min(dp[i][1].ff,dp[i-1][1].ff+1);
            dp[i][1].ss=max(dp[i][1].ss,dp[i-1][1].ss+1);
        }
        if(b[i]>=a[i-1]){
            dp[i][1].ff=min(dp[i][1].ff,dp[i-1][0].ff+1);
            dp[i][1].ss=max(dp[i][1].ss,dp[i-1][0].ss+1);
        }
    }
    int pos=n*2,cnt=n,tp=-1;
    if(dp[n*2][0].ff<=n && n<=dp[n*2][0].ss)tp=0;
    else if(dp[n*2][1].ff<=n && n<=dp[n*2][1].ss)tp=1;
    if(tp==-1){
        cout<<-1<<"\n";
        return 0;
    }
    string ans="";
    while(pos>=1){
        if(tp==0){
            ans+='A';
            if(a[pos]>=a[pos-1] && dp[pos-1][0].ff<=cnt && cnt<=dp[pos-1][0].ss)tp=0;
            else tp=1;
        }
        else{
            ans+='B';
            cnt--;
            if(b[pos]>=a[pos-1] && dp[pos-1][0].ff<=cnt && cnt<=dp[pos-1][0].ss)tp=0;
            else tp=1;
            
        }
        pos--;
    }
    reverse(all(ans));
    cout<<ans<<"\n";
}

/*
 2 5 4 9 15 11
 6 7 6 8 12 14
 1 0 0 0
 1 0 0 0
 0 0 0 0
 0 1 0 0
 0 1 1 0
 0 0 0 0

 0 1 0 0
 0 1 1 0
 0 1 0 0
 0 0 1 0
 0 0 1 1
 0 0 0 1
*/

• Subtask 1: 11 / 11
• Subtask 2: 89 / 89