제출 #1259609

#제출 시각아이디문제언어결과실행 시간메모리
1259609nqknhtPotemkin cycle (CEOI15_indcyc)C++20
100 / 100
207 ms91768 KiB
#include <bits/stdc++.h> #define ll long long #define ull unsigned long long #define dl double #define st first #define nd second #define II pair <int, int> using namespace std; const int N = 1 + 1e3; const int inf = 7 + 1e9; struct Edge { int u, v; }; int s = -1, t = -1; vector <Edge> e; vector <int> deg, vis, p; vector <vector <int>> adj; void dfs(int u) { if (s >= 0) return; vis[u] = 1; for (int v : adj[u]) { if (!vis[v]) { p[v] = u; // cout << "- " << u << ' ' << v << '\n'; dfs(v); } else if (vis[v] == 1) { s = u; t = v; } if (s >= 0) return; } vis[u] = 2; } int main() { #define TASKNAME "" ios_base :: sync_with_stdio (0); cin.tie (0); if ( fopen( TASKNAME".inp", "r" ) ) { freopen (TASKNAME".inp", "r", stdin); freopen (TASKNAME".out", "w", stdout); } int n, m; cin >> n >> m; e.resize(2 * m + 2); vector <vector <int>> f(n + 1, vector <int> (n + 1, 0)); for (int i = 1; i <= m; i ++) { cin >> e[i].u >> e[i].v; f[e[i].u][e[i].v] = i * 2; f[e[i].v][e[i].u] = i * 2 + 1; } adj.resize(2 * m + 2); for (int i = 1; i <= m; i ++) { int u = e[i].u, v = e[i].v; for (int w = 1; w <= n; w ++) if (w != u && w != v) { if (f[v][w] && !f[u][w]) adj[i * 2].push_back(f[v][w]); if (f[u][w] && !f[v][w]) adj[i * 2 + 1].push_back(f[u][w]); } } for (int i = m; i > 0; i --) { e[i * 2] = e[i]; e[i * 2 + 1] = {e[i].v, e[i].u}; } vis.assign(2 * m + 2, 0); p.assign(2 * m + 2, 0); for (int i = 2; i < m * 2 + 2; i ++) if (!vis[i]) { p[i] = 0; dfs(i); if (s >= 0) break; } if (s < 0) { cout << "no"; return 0; } vector <int> c; c.push_back(e[s].u); while (s != t) { s = p[s]; c.push_back(e[s].u); } for (int i = (int)c.size() - 1; i >= 0; i --) for (int j = i + 3; j < c.size(); j ++) if (f[c[i]][c[j]]) { for (int u = i; u <= j; u ++) cout << c[u] << ' '; return 0; } return 0; }

컴파일 시 표준 에러 (stderr) 메시지

indcyc.cpp: In function 'int main()':
indcyc.cpp:48:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   48 |         freopen (TASKNAME".inp", "r", stdin);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~
indcyc.cpp:49:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   49 |         freopen (TASKNAME".out", "w", stdout);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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