Submission #1264661

#TimeUsernameProblemLanguageResultExecution timeMemory
1264661minggaNetwork (BOI15_net)C++20
0 / 100
6 ms12100 KiB
// Author: caption_mingle #include "bits/stdc++.h" using namespace std; #define ln "\n" #define pb push_back #define fi first #define se second #define all(x) (x).begin(), (x).end() #define sz(x) ((int)(x).size()) #define ll long long const int mod = 1e9 + 7; const int inf = 2e9; const int N = 5e5 + 7; int n, in[N], out[N], timer; vector<int> g[N]; void dfs(int u, int p) { in[u] = ++timer; for(int v : g[u]) { if(v == p) continue; dfs(v, u); } } signed main() { cin.tie(0) -> sync_with_stdio(0); #define task "" 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].pb(v); g[v].pb(u); } dfs(1, 0); vector<int> vec; int dak = 0; for(int i = 1; i <= n; i++) { if(sz(g[i]) == 1) vec.pb(i); else dak = i; } sort(all(vec), [&](int x, int y) { return in[x] < in[y]; }); cout << (sz(vec) + 1) / 2 << ln; for(int i = 0; i < sz(vec) / 2; i++) { cout << vec[i] << ' ' << vec[sz(vec) - i - 1] << ln; } if(sz(vec) & 1) { cout << vec[sz(vec) / 2] << ' ' << vec[0] << ln; } cerr << "\nTime: " << clock() * 1000 / CLOCKS_PER_SEC; }

Compilation message (stderr)

net.cpp: In function 'int main()':
net.cpp:31:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   31 |                 freopen(task ".INP", "r", stdin);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
net.cpp:32:24: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   32 |                 freopen(task ".OUT", "w", stdout);
      |                 ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
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