Submission #894739

#	Submission time	Handle	Problem	Language	Result	Execution time	Memory
894739	2023-12-28T20:30:26 Z	beaboss	Building 4 (JOI20_building4)	C++14	100 / 100	185 ms	42020 KB

building4

// Source: https://oj.uz/problem/view/JOI20_building4
// 

#include "bits/stdc++.h"

using namespace std;

#define s second
#define f first
#define pb push_back

typedef long long ll;

typedef pair<int, int> pii;
typedef vector<pii> vpii;

typedef vector<int> vi;

#define FOR(i, a, b) for (int i = (a); i<b; i++)

bool ckmin(int& a, int b){ return b < a ? a = b, true : false; }

bool ckmax(int& a, int b){ return b > a ? a = b, true : false; }

const int N = (5e5 + 10) * 2;

int a[N];
int b[N];
int c[N];
int oc[N];

int swaps[N]; // -1 if not possible, 1 if dependent, 2 if independent

int cnt = 0;

bool flipped=false;

int n;

char rev(char ff) {
	if (ff == 'A') {
		cnt--;
		return 'B';
	}
	else {
		cnt++;
		return 'A';
	}
}
string chk(string s) {
	if (flipped) {
		FOR(i, 0, n) s[i] = rev(s[i]);
	}

	int prv = -1;

	FOR(i, 0, n) {
		if (s[i] == 'A') {
			assert(a[i] >= prv);
			prv = a[i];
		} else {
			assert(b[i] >= prv);
			prv = b[i];
		}
	}

	return s;
}

// int count(string s, char c) {
// 	int res = 0;
// 	FOR(i, 0, n) if (c == s[i]) res++;
// 	return res;
// }

int main() {
	ios::sync_with_stdio(false);
	cin.tie(nullptr);

	
	cin >> n;

	n *= 2;

	FOR(i, 0, n) {
		cin >> a[i];
	}
	FOR(i, 0, n) cin >> b[i];

	string ans;

	c[0] = min(a[0], b[0]);
	oc[0] = max(a[0], b[0]);

	if (c[0] == a[0]) {
		cnt++;
		ans += 'A';
	}
	else ans += 'B';

	for (int i = 1; i < n; i++) {
		if (min(a[i], b[i]) >= c[i-1]) {
			c[i] = min(a[i], b[i]);
			oc[i] = max(a[i], b[i]);
		} else if (max(a[i], b[i]) >= c[i-1]) {
			swaps[i]=-1;
			c[i] = max(a[i], b[i]);
			oc[i] = min(a[i], b[i]);

		} else {
			cout << -1 << endl;
			return 0;
		}

		if (c[i] == a[i]) {
			cnt++;
			ans += 'A';
		}
		else ans += 'B';
	}

	if (cnt == n/2) {
		cout << ans << endl;
		return 0;
	}


	
	if (cnt > n/2) {
		flipped=true;
		FOR(i, 0, n) ans[i] = rev(ans[i]);
	}


	c[n] = 1e9 + 10;
	// cout << cnt << endl;
	for (int i = n-1; i >= 0; i--) {
		
		assert(c[i] <= c[i+1]);
		if (swaps[i] == -1) continue;
		if (oc[i] <= c[i + 1]) swaps[i]=2; // independent
		else if (swaps[i + 1] != -1 && oc[i] <= oc[i + 1]) swaps[i]=1; // dependent
		else swaps[i]=-1;

		// cout << i << swaps[i] << endl;
	}




	int st = n-1;
	int mx = -1;
	int pos = -1;
	int res = 0;


	// assumes that A has less frequency

	for (int i = n-1; i >= 0; i--) {
		// cout << i << st << swaps[i] << endl;

		if (swaps[i] == -1 || swaps[i] == 2) {
			// cout << st << pos << mx << endl;
			if (i != st) {
				if (mx != -1) {
					// cout << pos << endl;
					for (int j = st; j >= pos; j--) {

						if (cnt != n/2) ans[j] = rev(ans[j]);
						else {
							cout << chk(ans) << endl;
							return 0;
						}

						if (cnt == n/2) {
							cout << chk(ans) << endl;
							return 0;
						}

					}
				}
			}
			st = i-1;
			mx = -1;
			res=0;

		}

		if (swaps[i] == 2) {
			st = i;
		}

		if (swaps[i] != -1) {
			res -= (ans[i] == 'A');
			res += (ans[i] == 'B');
			// cout << i << res << endl;
			if (res > mx) {
				pos = i;
				mx = res;
			}
		}

		// cout << i << st << mx <<  res << ans[i] << endl;
	}
	// cout << ans << endl;
	// cout << pos << endl;
	if (0 <= st && pos != -1) {
		for (int j = st; j >= pos; j--) {
			if (cnt != n/2) ans[j] = rev(ans[j]);
			else {
				cout << chk(ans) << endl;
				return 0;
			}

			if (cnt == n/2) {
				cout << chk(ans) << endl;
				return 0;
			}
		}
	}

	if (cnt == n/2) cout << chk(ans) << endl;

	else {

		cout << -1 << endl;
		// assert(false);
		return 0;
	}




}

Subtask #1

11.0 / 11.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	1 ms	8536 KB	Output is correct
2	Correct	1 ms	8540 KB	Output is correct
3	Correct	1 ms	8540 KB	Output is correct
4	Correct	1 ms	8540 KB	Output is correct
5	Correct	2 ms	8548 KB	Output is correct
6	Correct	2 ms	8540 KB	Output is correct
7	Correct	2 ms	8664 KB	Output is correct
8	Correct	2 ms	8540 KB	Output is correct
9	Correct	2 ms	8540 KB	Output is correct
10	Correct	2 ms	8540 KB	Output is correct
11	Correct	2 ms	8736 KB	Output is correct
12	Correct	2 ms	8540 KB	Output is correct
13	Correct	2 ms	8540 KB	Output is correct
14	Correct	2 ms	8664 KB	Output is correct
15	Correct	2 ms	8776 KB	Output is correct
16	Correct	2 ms	8732 KB	Output is correct
17	Correct	2 ms	8540 KB	Output is correct
18	Correct	2 ms	8744 KB	Output is correct
19	Correct	2 ms	8540 KB	Output is correct
20	Correct	2 ms	8540 KB	Output is correct
21	Correct	2 ms	8668 KB	Output is correct
22	Correct	2 ms	8536 KB	Output is correct
23	Correct	2 ms	8668 KB	Output is correct
24	Correct	2 ms	8536 KB	Output is correct
25	Correct	2 ms	8536 KB	Output is correct
26	Correct	2 ms	8540 KB	Output is correct
27	Correct	2 ms	8540 KB	Output is correct
28	Correct	2 ms	8672 KB	Output is correct
29	Correct	2 ms	8708 KB	Output is correct
30	Correct	2 ms	8540 KB	Output is correct
31	Correct	2 ms	8664 KB	Output is correct
32	Correct	2 ms	8540 KB	Output is correct
33	Correct	2 ms	8540 KB	Output is correct

Subtask #2

89.0 / 89.0

#	Verdict	Execution time	Memory	Grader output
1	Correct	1 ms	8536 KB	Output is correct
2	Correct	1 ms	8540 KB	Output is correct
3	Correct	1 ms	8540 KB	Output is correct
4	Correct	1 ms	8540 KB	Output is correct
5	Correct	2 ms	8548 KB	Output is correct
6	Correct	2 ms	8540 KB	Output is correct
7	Correct	2 ms	8664 KB	Output is correct
8	Correct	2 ms	8540 KB	Output is correct
9	Correct	2 ms	8540 KB	Output is correct
10	Correct	2 ms	8540 KB	Output is correct
11	Correct	2 ms	8736 KB	Output is correct
12	Correct	2 ms	8540 KB	Output is correct
13	Correct	2 ms	8540 KB	Output is correct
14	Correct	2 ms	8664 KB	Output is correct
15	Correct	2 ms	8776 KB	Output is correct
16	Correct	2 ms	8732 KB	Output is correct
17	Correct	2 ms	8540 KB	Output is correct
18	Correct	2 ms	8744 KB	Output is correct
19	Correct	2 ms	8540 KB	Output is correct
20	Correct	2 ms	8540 KB	Output is correct
21	Correct	2 ms	8668 KB	Output is correct
22	Correct	2 ms	8536 KB	Output is correct
23	Correct	2 ms	8668 KB	Output is correct
24	Correct	2 ms	8536 KB	Output is correct
25	Correct	2 ms	8536 KB	Output is correct
26	Correct	2 ms	8540 KB	Output is correct
27	Correct	2 ms	8540 KB	Output is correct
28	Correct	2 ms	8672 KB	Output is correct
29	Correct	2 ms	8708 KB	Output is correct
30	Correct	2 ms	8540 KB	Output is correct
31	Correct	2 ms	8664 KB	Output is correct
32	Correct	2 ms	8540 KB	Output is correct
33	Correct	2 ms	8540 KB	Output is correct
34	Correct	151 ms	32032 KB	Output is correct
35	Correct	153 ms	38812 KB	Output is correct
36	Correct	163 ms	39296 KB	Output is correct
37	Correct	166 ms	39952 KB	Output is correct
38	Correct	148 ms	39808 KB	Output is correct
39	Correct	146 ms	39092 KB	Output is correct
40	Correct	156 ms	41508 KB	Output is correct
41	Correct	147 ms	39476 KB	Output is correct
42	Correct	151 ms	37416 KB	Output is correct
43	Correct	185 ms	41572 KB	Output is correct
44	Correct	176 ms	41804 KB	Output is correct
45	Correct	167 ms	41804 KB	Output is correct
46	Correct	175 ms	41644 KB	Output is correct
47	Correct	159 ms	40668 KB	Output is correct
48	Correct	158 ms	40740 KB	Output is correct
49	Correct	174 ms	41512 KB	Output is correct
50	Correct	169 ms	41036 KB	Output is correct
51	Correct	181 ms	41032 KB	Output is correct
52	Correct	123 ms	30536 KB	Output is correct
53	Correct	127 ms	30540 KB	Output is correct
54	Correct	109 ms	30536 KB	Output is correct
55	Correct	109 ms	30280 KB	Output is correct
56	Correct	156 ms	42020 KB	Output is correct
57	Correct	139 ms	37028 KB	Output is correct
58	Correct	152 ms	37004 KB	Output is correct
59	Correct	147 ms	37184 KB	Output is correct
60	Correct	138 ms	36364 KB	Output is correct
61	Correct	150 ms	37708 KB	Output is correct
62	Correct	142 ms	37028 KB	Output is correct
63	Correct	147 ms	37704 KB	Output is correct
64	Correct	135 ms	36836 KB	Output is correct
65	Correct	141 ms	37708 KB	Output is correct