제출 #1250856

#제출 시각아이디문제언어결과실행 시간메모리
1250856tradzNetwork (BOI15_net)C++20
0 / 100
12 ms23876 KiB
#include <bits/stdc++.h> #define TIME (1.0 * clock() / CLOCKS_PER_SEC) #define For(i,a,b) for(int i = a; i <= b; i++) #define Ford(i,a,b) for(int i = a; i >= b; i--) #define ll long long #define ii pair<int,int> #define fi first #define se second #define all(v) v.begin(),v.end() #define RRH(v) v.resize(unique(all(v)) - v.begin()) using namespace std; const int N = 1e6+7; const int M = 1e9+7; const ll oo = 3e18; mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count()); long long GetRandom(long long l, long long r) { return uniform_int_distribution<long long> (l, r)(rng); } int n, cnt = 0; vector <int> g[N]; int timedfs = 0, tin[N], tout[N]; int dp[N]; void dfs(int u, int pre = 0) { tin[u] = tout[u] = ++timedfs; dp[u] = 1; for (int v: g[u]) { if (v == pre) continue; dfs(v, u); dp[u] += dp[v]; } tout[u] = timedfs; } int main() { ios::sync_with_stdio(0); cin.tie(0); #define TASK "" if (fopen (".inp", "r")) { freopen (".inp", "r", stdin); freopen (".out", "w", stdout); } if(fopen(TASK".inp", "r")) { freopen(TASK".inp", "r", stdin); freopen(TASK".out", "w", stdout); } cin >> n; for (int i = 1; i < n; i++) { int u, v; cin >> u >> v; g[u].push_back(v); g[v].push_back(u); } vector <pair <int, int>> ans; for (int i = 1; i <= n; i++) { if (g[i].size() >= 2) { dfs(i, 1); break; } } vector <pair <int, int>> ver; for (int i = 1; i <= n; i++) { if (dp[i] == 1) { ver.push_back({tin[i], i}); } } sort (all(ver)); for (int i = 0; i < ver.size(); i += 2) { int a = i; int b = (i + 1) % ver.size(); ans.push_back({ver[a].se, ver[b].se}); } cout << ans.size() << '\n'; for (int i = 0; i < ans.size(); i++) cout << ans[i].first << " " << ans[i].second << '\n'; cerr << "Time elapsed: " << TIME << " s.\n"; return 0; }

컴파일 시 표준 에러 (stderr) 메시지

net.cpp: In function 'int main()':
net.cpp:46:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   46 |         freopen (".inp", "r", stdin);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~
net.cpp:47:17: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   47 |         freopen (".out", "w", stdout);
      |         ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~
net.cpp:50:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |         freopen(TASK".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
net.cpp:51:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   51 |         freopen(TASK".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
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