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Submission #527965

# Submission time Handle Problem Language Result Execution time Memory
527965 2022-02-18T21:07:20 Z LucaDantas Alternating Current (BOI18_alternating) C++17
19 / 100
 44 ms 5568 KB 
#include <bits/stdc++.h>
using namespace std;

constexpr int maxn = 3e5+10;

int pref[maxn];
int mx = 0, ini_mx = 0, n, m;

struct Wire {
	int l, r, id;
	int sz() const { return r >= l ? r - l + 1 : r + (n - l + 1); }
	bool operator<(const Wire& o) const {
		if(l == o.l) return this->sz() > o.sz();
		if((l >= ini_mx) == (o.l >= ini_mx)) return l < o.l; // retorno o que tem o menor l já que eles são da mesma metade
		return l > o.l; // já que eles são de metades diferentes eu retorno o que tiver na metade maior
	}
} wr[maxn];

int pai[maxn];

int main() {
	scanf("%d %d", &n, &m);
	for(int i = 0; i < m; i++) {
		scanf("%d %d", &wr[i].l, &wr[i].r); wr[i].id = i;
		if(wr[i].l <= wr[i].r) {
			pref[wr[i].l]++;
			pref[wr[i].r+1]--;
		} else {
			pref[wr[i].l]++;
			pref[1]++;
			pref[wr[i].r+1]--;
		}
		
		if(wr[i].sz() > mx) {
			mx = wr[i].sz();
			ini_mx = wr[i].l;
		}
	}

	for(int i = 1; i <= n; i++) {
		pref[i] += pref[i-1];
		pref[i+n] = pref[i];
		if(pref[i] < 2) return puts("impossible"), 0;
	}

	sort(wr, wr+m);

	bool virou = 0;
	int fim = 0, aberto = -1;

	vector<Wire> brabos;

	memset(pai, -1, sizeof pai);
	for(int i = 0; i < m; i++) {
		auto [l, r, id] = wr[i];
		if(r < l) r += n;
		if(make_pair(virou, fim) < make_pair(min(l, r) < ini_mx, r)) {
			brabos.push_back(wr[i]);
			aberto = id;
			fim = r;
			virou |= min(l, r) < ini_mx;
		} else pai[id] = aberto;
	}

	/* puts("BRABOS: ");
	printf("Size: %ld\n", brabos.size());
	for(Wire x : brabos)
		printf("(%d %d %d) ", x.l, x.r, x.id);
	puts(""); */

	vector<int> ans(m);

	auto print = [&]() {
		for(int i = 0; i < m; i++)
			printf("%d", ans[i]);
		puts("");
		exit(0);
	};

	if(brabos[0].sz() == n) {
		ans[brabos[0].id] = 1;
		print();
	}

	if(brabos.size() % 2 == 0) {
		for(int i = 0; i < brabos.size(); i++)
			ans[brabos[i].id] = i&1;
		
		for(int i = 0; i < m; i++)
			if(pai[i] != -1) ans[i] = 1^ans[pai[i]];

		print();
	}

	sort(brabos.begin(), brabos.end(), [](const Wire& a, const Wire& b) { return a.l < b.l; });

	for(int i = 0; i < brabos.size(); i++) {
		auto nxt = [&](int x) { return (x+1) % brabos.size(); };
		auto eu = brabos[i], prox = brabos[nxt(i)];
		int l = prox.l, r = eu.r;
		
		if(r < l) r += n;

		bool tem = 1;
		for(int j = l; j <= r; j++)
			tem &= pref[j] >= 3;

		auto no_intersection = [](Wire a, Wire b) {
			if(a.r < a.l) a.r += n;
			if(b.r < b.l) b.r += n;

			if(a.r < b.l) return 1;
			return 0;
		};
		if(tem || no_intersection(eu, prox)) {
			// printf("BOM %d | %d %d\n", i, l, r);

			bool opa = 1;
			ans[ brabos[i].id ] = opa;

			for(int j = nxt(i); j != i; j = nxt(j)) {
				ans[ brabos[j].id ] = opa;
				opa ^= 1;
			}

			for(int i = 0; i < m; i++)
				if(pai[i] != -1) ans[i] = 1^ans[pai[i]];

			print();
		}
	}

	puts("impossible");
}

Compilation message

alternating.cpp: In function 'int main()':
alternating.cpp:86:20: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<Wire>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   86 |   for(int i = 0; i < brabos.size(); i++)
      |                  ~~^~~~~~~~~~~~~~~
alternating.cpp:97:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<Wire>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   97 |  for(int i = 0; i < brabos.size(); i++) {
      |                 ~~^~~~~~~~~~~~~~~
alternating.cpp:22:7: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   22 |  scanf("%d %d", &n, &m);
      |  ~~~~~^~~~~~~~~~~~~~~~~
alternating.cpp:24:8: warning: ignoring return value of 'int scanf(const char*, ...)' declared with attribute 'warn_unused_result' [-Wunused-result]
   24 |   scanf("%d %d", &wr[i].l, &wr[i].r); wr[i].id = i;
      |   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Subtask #1
0 / 13.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 1488 KB Output is correct
2 Correct 1 ms 1456 KB Output is correct
3 Correct 1 ms 1448 KB Output is correct
4 Correct 1 ms 1488 KB Output is correct
5 Correct 1 ms 1488 KB Output is correct
6 Correct 1 ms 1488 KB Output is correct
7 Correct 1 ms 1360 KB Output is correct
8 Correct 0 ms 208 KB Output is correct
9 Correct 1 ms 1360 KB Output is correct
10 Correct 1 ms 208 KB Output is correct
11 Correct 0 ms 208 KB Output is correct
12 Incorrect 1 ms 1488 KB no wires in direction 1 between segments 6 and 7
13 Halted 0 ms 0 KB -

Subtask #2
0 / 20.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 1488 KB Output is correct
2 Correct 1 ms 1456 KB Output is correct
3 Correct 1 ms 1448 KB Output is correct
4 Correct 1 ms 1488 KB Output is correct
5 Correct 1 ms 1488 KB Output is correct
6 Correct 1 ms 1488 KB Output is correct
7 Correct 1 ms 1360 KB Output is correct
8 Correct 0 ms 208 KB Output is correct
9 Correct 1 ms 1360 KB Output is correct
10 Correct 1 ms 208 KB Output is correct
11 Correct 0 ms 208 KB Output is correct
12 Incorrect 1 ms 1488 KB no wires in direction 1 between segments 6 and 7
13 Halted 0 ms 0 KB -

Subtask #3
0 / 22.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 1488 KB Output is correct
2 Correct 1 ms 1456 KB Output is correct
3 Correct 1 ms 1448 KB Output is correct
4 Correct 1 ms 1488 KB Output is correct
5 Correct 1 ms 1488 KB Output is correct
6 Correct 1 ms 1488 KB Output is correct
7 Correct 1 ms 1360 KB Output is correct
8 Correct 0 ms 208 KB Output is correct
9 Correct 1 ms 1360 KB Output is correct
10 Correct 1 ms 208 KB Output is correct
11 Correct 0 ms 208 KB Output is correct
12 Incorrect 1 ms 1488 KB no wires in direction 1 between segments 6 and 7
13 Halted 0 ms 0 KB -

Subtask #4
19.0 / 19.0

# Verdict Execution time Memory Grader output
1 Correct 27 ms 4772 KB Output is correct
2 Correct 2 ms 2252 KB Output is correct
3 Correct 9 ms 1840 KB Output is correct
4 Correct 15 ms 3632 KB Output is correct
5 Correct 37 ms 5412 KB Output is correct
6 Correct 20 ms 2992 KB Output is correct
7 Correct 40 ms 5100 KB Output is correct
8 Correct 2 ms 2252 KB Output is correct
9 Correct 2 ms 2124 KB Output is correct
10 Correct 40 ms 5568 KB Output is correct
11 Correct 30 ms 4640 KB Output is correct
12 Correct 34 ms 4760 KB Output is correct
13 Correct 1 ms 1048 KB Output is correct
14 Correct 1 ms 972 KB Output is correct
15 Correct 44 ms 5108 KB Output is correct
16 Correct 11 ms 2220 KB Output is correct
17 Correct 39 ms 4952 KB Output is correct
18 Correct 34 ms 4060 KB Output is correct
19 Correct 2 ms 716 KB Output is correct
20 Correct 43 ms 5336 KB Output is correct

Subtask #5
0 / 26.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 1488 KB Output is correct
2 Correct 1 ms 1456 KB Output is correct
3 Correct 1 ms 1448 KB Output is correct
4 Correct 1 ms 1488 KB Output is correct
5 Correct 1 ms 1488 KB Output is correct
6 Correct 1 ms 1488 KB Output is correct
7 Correct 1 ms 1360 KB Output is correct
8 Correct 0 ms 208 KB Output is correct
9 Correct 1 ms 1360 KB Output is correct
10 Correct 1 ms 208 KB Output is correct
11 Correct 0 ms 208 KB Output is correct
12 Incorrect 1 ms 1488 KB no wires in direction 1 between segments 6 and 7
13 Halted 0 ms 0 KB -