Submission #565243

#	Time	Username	Problem	Language	Result	Execution time	Memory
565243		errorgorn	Building 4 (JOI20_building4)	C++17	100 / 100	261 ms	68880 KiB

building4

// Super Idol的笑容
//    都没你的甜
//  八月正午的阳光
//    都没你耀眼
//  热爱105°C的你
// 滴滴清纯的蒸馏水

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/rope>
using namespace std;
using namespace __gnu_pbds;
using namespace __gnu_cxx;

#define int long long
#define ll long long
#define ii pair<ll,ll>
#define iii pair<ii,ll>
#define fi first
#define se second
#define endl '\n'
#define debug(x) cout << #x << ": " << x << endl

#define pub push_back
#define pob pop_back
#define puf push_front
#define pof pop_front
#define lb lower_bound
#define ub upper_bound

#define rep(x,start,end) for(int x=(start)-((start)>(end));x!=(end)-((start)>(end));((start)<(end)?x++:x--))
#define all(x) (x).begin(),(x).end()
#define sz(x) (int)(x).size()

#define indexed_set tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update>
//change less to less_equal for non distinct pbds, but erase will bug

mt19937 rng(chrono::system_clock::now().time_since_epoch().count());

int n;
int arr[1000005][2];
ii memo[1000005][2];

signed main(){
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	cin.exceptions(ios::badbit | ios::failbit);
	
	cin>>n;
	rep(x,1,2*n+1) cin>>arr[x][0];
	rep(x,1,2*n+1) cin>>arr[x][1];
	
	rep(x,0,1000005) rep(y,0,2) memo[x][y]={1e9,-1e9};
	memo[1][0]={0,0};
	memo[1][1]={1,1};
	
	rep(x,1,2*n) rep(a,0,2) rep(b,0,2) if (arr[x][a]<=arr[x+1][b]){
		memo[x+1][b]={
			min(memo[x+1][b].fi,memo[x][a].fi+b),
			max(memo[x+1][b].se,memo[x][a].se+b)
		};
	}
	
	int py=-1;
	rep(x,0,2) if (memo[2*n][x].fi<=n && n<=memo[2*n][x].se) py=x;
	
	if (py==-1){
		cout<<"-1"<<endl;
		return 0;
	}
	
	string ans="";
	
	ans+='A'+py;
	
	int curr=n;
	rep(x,2*n,1){
		if (py) curr--;
		rep(y,0,2) if (arr[x][y]<=arr[x+1][py] && memo[x][y].fi<=curr && curr<=memo[x][y].se){
			py=y;
			break;
		}
		ans+='A'+py;
	}
	
	reverse(all(ans));
	cout<<ans<<endl;
}

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