Submission #231643

#	Time	Username	Problem	Language	Result	Execution time	Memory
231643		syy	Building 4 (JOI20_building4)	C++17	100 / 100	323 ms	52232 KiB

building4

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
#define FOR(i, a, b) for(ll i = (ll)a; i <= (ll)b; i++)
#define DEC(i, a, b) for(ll i = (ll)a; i >= (ll)b; i--)
typedef pair<ll, ll> pi;
#define f first
#define s second
typedef vector<ll> vi;
typedef vector<pi> vpi;
#define pb push_back
#define all(v) v.begin(), v.end()
#define fastio ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)

const ll INF = 1e18 + 100;
const pi PINF = pi(INF, INF);
ll n, a[1000005], b[1000005], v, rv;
pi range[1000005][2]; //0 A, 1 B
string ans;
bool A;

inline pi add(pi a, ll v) {
	return pi(a.f+v, a.s+v);
}

inline pi merge(pi a, pi b) {
	if (a == PINF) return b;
	if (b == PINF) return a;
	return pi(min(a.f, b.f), max(a.s, b.s));
}

inline bool inter(pi a, int b) {
	return (a.f <= b and b <= a.s);
}

void fail() {
	cout << -1;
	exit(0);
}

int main() {
	fastio; cin >> n;
	FOR(i, 1, 2*n) cin >> a[i];
	FOR(i, 1, 2*n) cin >> b[i];
	range[1][0] = pi(1, 1);
	range[1][1] = pi(-1, -1);
	FOR(i, 2, 2*n) {
		range[i][0] = PINF; range[i][1] = PINF;
		if (a[i] >= a[i-1] and range[i-1][0] != PINF) range[i][0] = add(range[i-1][0], 1);
		if (a[i] >= b[i-1] and range[i-1][1] != PINF) range[i][0] = merge(range[i][0], add(range[i-1][1], 1));
		if (b[i] >= a[i-1] and range[i-1][0] != PINF) range[i][1] = add(range[i-1][0], -1);
		if (b[i] >= b[i-1] and range[i-1][1] != PINF) range[i][1] = merge(range[i][1], add(range[i-1][1], -1));
	}
	v = -1, A = 0, rv = INF;
	DEC(i, 2*n+1, 2) {
		v = v + (A ? -1 : 1);
		if (inter(range[i-1][0], v) and rv >= a[i-1]) A = 1;
		else if (inter(range[i-1][1], v) and rv >= b[i-1]) A = 0;
		else fail();
		ans += (A ? 'A' : 'B');
		rv = (A ? a[i-1] : b[i-1]);
	}
	reverse(all(ans));
	cout << ans;
}

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