Submission #530579

#	Time	Username	Problem	Language	Result	Execution time	Memory
530579		cheissmart	Building 4 (JOI20_building4)	C++14	100 / 100	266 ms	44072 KiB

building4

#include <bits/stdc++.h>
#define IO_OP ios::sync_with_stdio(0), cin.tie(0)
#define F first
#define S second
#define V vector
#define PB push_back
#define EB emplace_back
#define MP make_pair
#define SZ(v) int((v).size())
#define ALL(v) (v).begin(), (v).end()

using namespace std;

typedef long long ll;
typedef pair<int, int> pi;
typedef V<int> vi;

const int INF = 1e9 + 7;

signed main()
{
	IO_OP;
		
	int n;
	cin >> n;
	n *= 2;
	V<array<int, 2>> a(n);
	for(int i = 0; i < n; i++)
		cin >> a[i][0];
	for(int i = 0; i < n; i++)
		cin >> a[i][1];
	V<array<int, 2>> l(n, {INF, INF}), r(n, {-INF, -INF});
	auto upd = [&] (int i, int j, int L, int R) {
		l[i][j] = min(l[i][j], L);
		r[i][j] = max(r[i][j], R);
	};
	upd(0, 0, 0, 0);
	upd(0, 1, 1, 1);
	for(int i = 1; i < n; i++) {
		for(int j = 0; j < 2; j++) if(l[i - 1][j] <= r[i - 1][j]) {
			for(int k = 0; k < 2; k++) {
				if(a[i - 1][j] <= a[i][k]) {
					int L = l[i - 1][j] + k, R = r[i - 1][j] + k;
					upd(i, k, L, R);
				}
			}
		}
	}
	int j = -1;
	for(int i = 0; i < 2; i++) {
		if(l[n - 1][i] <= n / 2 && n / 2 <= r[n - 1][i])
			j = i;
	}
	if(j == -1) {
		cout << -1 << '\n';
		return 0;
	}
	int i = n - 1, need = n / 2;
	string s;
	while(i >= 0) {
		assert(l[i][j] <= need && need <= r[i][j]);
		s += 'A' + j;
		need -= j;
		if(i == 0) break;
		for(int k = 0; k < 2; k++) {
			if(a[i][j] >= a[i - 1][k] && l[i - 1][k] <= need && need <= r[i - 1][k]) {
				j = k;
				break;				
			}
		}
		i--;
	}
	reverse(ALL(s));
	cout << s << '\n';
}

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