Submission #280359

#	Time	Username	Problem	Language	Result	Execution time	Memory
280359		spdskatr	Joker (BOI20_joker)	C++14	25 / 100	522 ms	19448 KiB

Joker

#include <cstdio>
#include <cstdlib>
#include <algorithm>
#include <vector>
#include <cstring>
#include <cassert>
#define fi first
#define se second

using namespace std;
typedef pair<int, int> pii;

int N, M, Q, seen[200005], col[200005];
vector<pii> graph[200005];

int dfs(int x, int l) {
	seen[x] = 1;
	for (pii p : graph[x]) {
		int v = p.fi, e = p.se;
		if (e >= l) {
			if (seen[v]) {
				if (col[v] == col[x]) return 1;
			} else {
				col[v] = !col[x];
				if (dfs(v, l)) return 1;
			}
		}
	}
	return 0;
}
int decide(int l) {
	for (int i = 1; i <= N; i++) if (!seen[i]) if (dfs(i, l)) return 1;
	return 0;
}

int main() {
	scanf("%d %d %d", &N, &M, &Q);
	for (int i = 1; i <= M; i++) {
		int a, b;
		scanf("%d %d", &a, &b);
		graph[a].push_back({ b, i });
		graph[b].push_back({ a, i });
	}
	int lo = 0, hi = M;
	while (lo + 1 < hi) {
		int mid = (lo + hi) / 2;
		memset(seen, 0, sizeof(seen));
		memset(col, 0, sizeof(col));
		if (decide(mid)) lo = mid;
		else hi = mid;
	}
	for (int q = 0; q < Q; q++) {
		int l, r;
		scanf("%d %d", &l, &r);
		assert(l == 1);
		if (r+1 >= hi) printf("NO\n");
		else printf("YES\n");
	}
}

Compilation message (stderr)

Joker.cpp: In function 'int main()':
Joker.cpp:37:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   37 |  scanf("%d %d %d", &N, &M, &Q);
      |  ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
Joker.cpp:40:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   40 |   scanf("%d %d", &a, &b);
      |   ~~~~~^~~~~~~~~~~~~~~~~
Joker.cpp:54:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   54 |   scanf("%d %d", &l, &r);
      |   ~~~~~^~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 6
• Subtask 2: 0 / 8
• Subtask 3: 25 / 25
• Subtask 4: 0 / 10
• Subtask 5: 0 / 22
• Subtask 6: 0 / 29