Submission #831215

#	Time	Username	Problem	Language	Result	Execution time	Memory
831215		NK_	Towers (NOI22_towers)	C++17	75 / 100	2100 ms	627616 KiB

Main

// Success consists of going from failure to failure without loss of enthusiasm
#include <bits/stdc++.h>

using namespace std;
 
#define nl '\n'
#define pb push_back
#define pf push_front

#define mp make_pair
#define f first
#define s second
#define sz(x) int(x.size())
 
template<class T> using V = vector<T>;
using pi = pair<int, int>;
using vi = V<int>;
using vpi = V<pi>;

using ll = long long;
using pl = pair<ll, ll>;
using vpl = V<pl>;
using vl = V<ll>;

using db = long double;

template<class T> using pq = priority_queue<T, V<T>, greater<T>>;

const int MOD = 1e9 + 7;
const ll INFL = ll(1e16) + 10;

int main() {
	cin.tie(0)->sync_with_stdio(0);
	
	int N; scanf("%d", &N);
	vpi A(N); for(auto& x : A) {
		scanf("%d %d", &x.f, &x.s);
	}

	int ROWS = 0, COLS = 0;
	for(int t = 0; t < 2; t++) {
		vi X; for(auto& x : A) X.pb(x.f); 

		sort(begin(X), end(X)); X.erase(unique(begin(X), end(X)), end(X));

		for(auto& x : A) {
			x.f = lower_bound(begin(X), end(X), x.f) - begin(X);
			// cerr << x.f << " " << x.s << endl;
			swap(x.f, x.s);
		}
		// cerr << endl;
		ROWS = sz(X); swap(ROWS, COLS);
	}

	map<ll, int> IDX; for(int i = 0; i < N; i++) {
		// cerr << A[i].f << " " << A[i].s << " is " << i << endl;
		IDX[A[i].f * 1LL * COLS + A[i].s] = i;
	}

	V<vi> C(COLS);
	for(int i = 0; i < N; i++) C[A[i].s].pb(A[i].f);
	for(int i = 0; i < COLS; i++) sort(begin(C[i]), end(C[i]));

	V<deque<pi>> R(ROWS); 

	vi POS(2 * COLS, -1); int Q = 0;
	vi stk;
	function<void(int)> update = [&](int X) {
		stk.pb(X);

		while(sz(stk)) {
			Q++; assert(Q <= 3 * N);

			int x = stk.back(); stk.pop_back(); 
			if (POS[x] == -1) continue;
			// cerr << "UPDATE " << x << endl;

			// 2*y+c => y is col # and c is dir (0 - dwn (+1), 1 - up (-1));
			int y = x / 2, dir = (x % 2 ? -1 : +1);
			while(1) {
				if (POS[x] < 0 || POS[x] >= sz(C[y])) {
					POS[x] = -1; break;
				}

				if (POS[2*y] == POS[2*y+1]) {
					POS[x] = -1;
					break; // stop because same as other one
				}

				int r = C[y][POS[x]]; // row

				// cerr << r << " " << y << " " << x << " " << dir << endl;

				if (sz(R[r]) == 0) {
					// cerr << "ADDED " << r << endl;
					R[r].pb(mp(y, x));
					break;
				}

				// check if you can put it in
				if (R[r].back().f < y) { // sz(R[r]) == 2 put in at the back
					// cerr << "ADDED TO BACK " << r << endl;
					if (sz(R[r]) == 2) {
						int i = R[r].back().s; R[r].pop_back(); 
						R[r].pb(mp(y, x));	
						// cerr << "MUST UPDATE " << i << endl;
						stk.pb(i); 
					} else R[r].pb(mp(y, x));	
					break;
				}

				if (y < R[r].front().f) { // sz(R[r]) == 2 put in at the front
					// cerr << "ADDED TO FRONT " << r << endl;
					if (sz(R[r]) == 2) {
						int i = R[r].front().s; R[r].pop_front(); 
						R[r].pf(mp(y, x));
						// cerr << "MUST UPDATE " << i << endl;
						stk.pb(i);
					} else R[r].pf(mp(y, x));
					break;
				}

				POS[x] += dir;
			}
		}
	};


	for(int c = 0; c < COLS; c++) {
		POS[2 * c] = 0; 
		update(2 * c); 

		POS[2 * c + 1] = sz(C[c]) - 1;
		update(2 * c + 1);
	}

	vpi take;
	for(int i = 0; i < 2 * COLS; i++) {
		int c = i / 2; 
		if (0 <= POS[i] && POS[i] < sz(C[c])) {
			// cerr << C[c][POS[i]] << " " << c << endl;
			take.pb(mp(C[c][POS[i]], c));
		}
	}

	string ans(N, '0');
	for(auto& p : take) {
		// cerr << p.f * 1LL * COLS + p.s << endl;
		ans[IDX[p.f * 1LL * COLS + p.s]] = '1';
	}

	cout << ans << endl;
	
	auto check = [&]() {
		vi good(N);

		map<int, int> ROW, COL;
		for(int i = 0; i < N; i++) if (ans[i] == '1') {
			ROW[A[i].f]++; COL[A[i].s]++;
		} 

		for(auto p : ROW) if (p.s > 2) assert(false);
		for(auto p : COL) if (p.s > 2) assert(false);

		for(int i = 0; i < N; i++) {
			if (ans[i] == '0') {
				for(int a = 0; a < N; a++) for(int b = 0; b < N; b++) {
					if (a == b) continue;
					if (ans[a] != '1' || ans[b] != '1') continue;
					if ((A[a].f != A[b].f) ^ (A[a].s != A[b].s) ^ 1) continue;

					int l = min(A[a].f, A[b].f), r = max(A[a].f, A[b].f);
					int L = min(A[a].s, A[b].s), R = max(A[a].s, A[b].s);

					// cerr << a << " " << b << endl;
					// cerr << l << " " << r << endl;
					// cerr << L << " " << R << endl;
					// cerr << endl;

					if (l <= A[i].f && A[i].f <= r && L <= A[i].s && A[i].s <= R) {
						good[i] = 1;
					}
				}
			} else good[i] = 1;
		}

		assert(accumulate(begin(good), end(good), 0) == N);
	};

	// check();


    return 0;
} 	

Compilation message (stderr)

Main.cpp: In function 'int main()':
Main.cpp:154:7: warning: variable 'check' set but not used [-Wunused-but-set-variable]
  154 |  auto check = [&]() {
      |       ^~~~~
Main.cpp:35:14: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   35 |  int N; scanf("%d", &N);
      |         ~~~~~^~~~~~~~~~
Main.cpp:37:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   37 |   scanf("%d %d", &x.f, &x.s);
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 11 / 11
• Subtask 3: 7 / 7
• Subtask 4: 0 / 6
• Subtask 5: 31 / 31
• Subtask 6: 21 / 21
• Subtask 7: 0 / 19