Submission #1048831

#	Time	Username	Problem	Language	Result	Execution time	Memory
1048831		1L1YA	Building 4 (JOI20_building4)	C++17	100 / 100	137 ms	45484 KiB

building4

//1L1YA

#include<bits/stdc++.h>
using namespace std;

//#pragma GCC optimize ("O3,unrool-loops")
//#pragma GCC target("avx2,bmi,bmi2,lzcnt,popcnt")

typedef long long       ll;
typedef pair<ll,ll>     pll;
typedef pair<int,int>   pii;

#define Pb              push_back
#define F               first
#define S               second
#define endl            '\n'
#define sep             ' '
#define all(x)          x.begin(),x.end()
#define al(x,n)         x+1,x+n+1
#define SZ(x)           ((int)x.size())
#define lc              (id<<1)
#define rc              (lc|1)
#define mid             (l+r>>1)
#define dokme(x)        cout << x << endl, exit(0)
#define sik(x)          cout << x << endl;continue;
#define FastIO          ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define FileIO          freopen("input.txt","r",stdin);freopen("output.txt","w",stdout);

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

const ll oo=1e18;
const int mod=1e9+7;
const int inf=1e9+111;
const int N=1e6+11;
const int lg=23;

int n,a[N][2];
pii dp[N][2];
string ans;

int main(){
	FastIO

	cin >> n;
	for(int j=0;j<2;j++)
		for(int i=1;i<=n<<1;i++)
			cin >> a[i][j];
	dp[1][0]={0,0};
	dp[1][1]={1,1};
	for(int i=2;i<=n<<1;i++){
		dp[i][0]=dp[i][1]={inf,-1};
		for(int j=0;j<2;j++)
			for(int k=0;k<2;k++)
				if(a[i-1][j]<=a[i][k])
					dp[i][k]={min(dp[i][k].F,dp[i-1][j].F+k),max(dp[i][k].S,dp[i-1][j].S+k)};
	}
	if(!(dp[n<<1][0].F<=n && n<=dp[n<<1][0].S) && !(dp[n<<1][1].F<=n && n<=dp[n<<1][1].S))	dokme(-1);
	int c=n,nxt=inf;
	for(int i=n<<1;i;i--)
		if(dp[i][0].F<=c && c<=dp[i][0].S && a[i][0]<=nxt)	ans+="A",nxt=a[i][0];
		else	ans+="B",nxt=a[i][1],c--;
	reverse(all(ans));
	cout << ans << endl;

	return 0;
}

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