Submission #54876

#	Time	Username	Problem	Language	Result	Execution time	Memory
54876		ics0503	Potemkin cycle (CEOI15_indcyc)	C++17	40 / 100	266 ms	15412 KiB

indcyc

#include<stdio.h>
#include<algorithm>
#include<vector>
#include<set>
using namespace std;
vector<int>edge[1212], E[1212];
int depth[1212], is_gone_dfs1[1212];
set<pair<int, int>>L[1212];  set<int>M[1212];
void dfs1(int w,int dep,int bef) {
	depth[w] = dep; is_gone_dfs1[w] = 1;
	for (int i = 0; i < edge[w].size(); i++) {
		int next = edge[w][i];
		if (is_gone_dfs1[next]) {
			if(next==bef || depth[next] > depth[w])continue;
			L[w].insert({ depth[next],next });
			continue;
		}
		E[w].push_back(next);
		dfs1(next, dep + 1, w);
	}
}
int stdep, D[1212], st, go[1212], R[1212], cck;
int dfs2(int w, int bef) {
	set<pair<int, int>>::iterator it = L[w].lower_bound({ stdep + 1,-1e9 });
	if (bef != -1 && it == L[w].end())D[w] = D[bef] + 1, go[w] = bef, R[w] = R[bef];
	if (bef != -1 && it != L[w].end())D[w] = D[it->second] + 1, go[w] = it->second, R[w] = R[it->second];
	if (M[w].find(st) != M[w].end()) {
		if (D[w] >= 4)return w;
		if (D[w] == 3) {
			int x = go[w];
			for (int i = 0; i < edge[w].size(); i++) {
				if (D[edge[w][i]] >= 3 && R[x] != R[edge[w][i]]) {
					go[w] = edge[w][i];
					return w;
				}
			}
		}
		D[w] = 2, go[w] = st;
		R[w] = w;
	}
	for (int i = 0; i < E[w].size(); i++){
		int next = E[w][i];
		int k = dfs2(next, w);
		if (k) return k;
	}
	return 0;
}
int main() {
	int n, m; scanf("%d%d", &n, &m);
	int i, j;
	for (i = 0; i < m; i++) {
		int s, e; scanf("%d%d", &s, &e);
		edge[s].push_back(e); M[s].insert(e);
		edge[e].push_back(s); M[e].insert(s);
	}
	for (i = 1; i <= n; i++) {
		if (is_gone_dfs1[i])continue;
		dfs1(i, 1, -1);
	}
	for (i = 1; i <= n; i++) {
		D[i] = 1; R[i] = st = i; stdep = depth[i];
		int now = dfs2(i, -1);
		if (now) {
			while (now != i) {
				printf("%d ", now);
				now = go[now];
			}
			printf("%d ", i);
			return 0;
		}
		for (j = 1; j <= n; j++)D[j] = R[j] = go[j] = 0;
	}
	printf("no");
	return 0;
}

Compilation message (stderr)

indcyc.cpp: In function 'void dfs1(int, int, int)':
indcyc.cpp:11:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < edge[w].size(); i++) {
                  ~~^~~~~~~~~~~~~~~~
indcyc.cpp: In function 'int dfs2(int, int)':
indcyc.cpp:31:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (int i = 0; i < edge[w].size(); i++) {
                    ~~^~~~~~~~~~~~~~~~
indcyc.cpp:41:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0; i < E[w].size(); i++){
                  ~~^~~~~~~~~~~~~
indcyc.cpp: In function 'int main()':
indcyc.cpp:49:17: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  int n, m; scanf("%d%d", &n, &m);
            ~~~~~^~~~~~~~~~~~~~~~
indcyc.cpp:52:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   int s, e; scanf("%d%d", &s, &e);
             ~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 10 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10