Submission #261865

#	Time	Username	Problem	Language	Result	Execution time	Memory
261865		Atalasion	Building 4 (JOI20_building4)	C++14	0 / 100	2 ms	512 KiB

building4

#include <bits/stdc++.h>

#define F first
#define S second
#define pb push_back
#define all(x) x.begin(), x.end()
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops,fast-math")

using namespace std;

typedef long long ll;
typedef pair<int, int> pii;
typedef vector<int> vi;

const int N = 1000000 + 10;
const int MOD = 1000000007;
const int LOG = 20;
const int INF = 1000000010;
const int delta = 11353;

pii dp[N][2];
int n, A[N], B[N], ans[N];

pii merge(pii x, pii y){
	return {min(x.F, y.F), max(x.S, y.S)};
}

int32_t main(){
	ios::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	cin >> n;
	for (int i = 1; i <= 2 * n; i++) cin >> A[i];
	for (int i = 1; i <= 2 * n; i++) cin >> B[i];
	dp[0][0] = {0, 0};
	for (int i = 1; i <= 2 * n; i++){
		if (min(A[i - 1], B[i - 1]) > max(A[i], B[i])) return cout << -1, 0;
		if (A[i] >= B[i - 1] && A[i] >= A[i - 1]) dp[i][0] = merge(dp[i - 1][0], dp[i - 1][1]);
		else if(A[i] >= B[i - 1]) dp[i][0] = dp[i - 1][1];
		else if(A[i] >= A[i - 1]) dp[i][0] = dp[i - 1][0];
		dp[i][0].F++, dp[i][0].S ++;
		if (B[i] >= B[i - 1] && B[i] >= A[i - 1]) dp[i][1] = merge(dp[i - 1][0], dp[i - 1][1]);
		else if(B[i] >= B[i - 1]) dp[i][1] = dp[i - 1][1];
		else if (B[i] >= A[i - 1]) dp[i][1] = dp[i - 1][0];
		//cout << dp[i][0].F << ' ' << dp[i][0].S << ' ' << dp[i][1].F << ' '  << dp[i][1].S << '\n';
	}
	if ((dp[2 * n][0].F <= n && dp[2 * n][0].S >= n) || (dp[2 * n][1].F <= n && dp[2 * n][1].S >= n)){
		pair<pii, int> Now;
		if (dp[2 * n][0].F <= n && dp[2 * n][0].S >= n) Now = {{2 * n, 0}, n};
		else Now = {{2 * n, 1}, n};
		while (Now.F.F != 0){
			int id = Now.F.F, u = Now.S;
			if (Now.F.S == 0){
				if (A[id - 1] <= A[id]){
					if (dp[id - 1][0].F <= (u - 1) && dp[id - 1][0].S >= (u - 1)) Now = {{id - 1, 0}, u - 1};
				}
				if (Now.F.F == id){
				 	Now = {{id - 1, 1}, u - 1};
				}
				ans[id] = 0;
			}else{
				if (A[id - 1] <= B[id]){
					if (dp[id - 1][0].F <= u && dp[id - 1][0].S >= u) Now = {{id - 1, 0}, u};
				}
				if (Now.F.F == id){
					Now = {{id - 1, 1}, u};
				}
				ans[id] = 1;
			}
		}
		for (int i = 1; i <= 2 * n; i++) cout << (ans[i]?"B":"A");
	}
	else cout << -1;
	return 0;
}

• Subtask 1: 0 / 11
• Subtask 2: 0 / 89