Submission #1087389

#TimeUsernameProblemLanguageResultExecution timeMemory
1087389smileTorrent (COI16_torrent)C++14
31 / 100
2070 ms28756 KiB
#include <bits/stdc++.h> #define smile "TDL." #define mp make_pair using namespace std; typedef pair<int, int> ii; typedef long long ll; const int N = (int) 3e5 + 10; int n, m; vector<int> g[N]; int M[3]; int f[N]; int c[N]; ii banned = mp(0,0); void dfs(int u, int pre) { vector<int> tmp; f[u] = 0; c[u] = 0; for (int v: g[u]) { if (v == pre || mp(min(u, v), max(u, v)) == banned) continue; dfs(v, u); c[u]++; tmp.push_back(f[v]); } sort(tmp.begin(), tmp.end(), greater<int>()); for (int i = 0; i < tmp.size(); i++) f[u] = max(f[u], tmp[i]+i+1); } namespace SUB2 { void solve() { dfs(M[0], M[0]); cout << f[M[0]]; } } namespace SUB4 { int trace[N]; void bfs(int s, int t) { queue<int> q; q.push(s); trace[s] = -1; while (!q.empty()) { int u = q.front(); q.pop(); for (int v: g[u]) { if (!trace[v]) { trace[v] = u; q.push(v); if (v == t) return; } } } } vector<ii> e; vector<int> tmp; int calc(int u, int v) { banned = mp(min(u, v), max(u,v)); dfs(M[0], M[0]); dfs(M[1], M[1]); int t1 = f[M[0]], t2 = f[M[1]]; if (t1 < t2) t1 += (c[M[0]] == t1); else if (t2 < t1) t2 += (c[M[1]] == t2); else if (c[M[0]] == t1 && c[M[1]] == t2) t1++; return max(t1, t2); } void T() { int tl = calc(tmp[0], tmp[1]), tr = calc(tmp[tmp.size()-2], tmp[tmp.size()-1]); int l = 1, r = tmp.size()-2; for (int i = 17; i >= 0; i--) { if (l + (1 << i) > r) continue; int j = l + (1 << i); int u = tmp[j], v = tmp[j-1]; if (calc(u, v) == tl) l += (1 << i); } for (int i = 17; i >= 0; i--) { if (r - (1 << i) < l) continue; int j = r - (1 << i); int u = tmp[j], v = tmp[j+1]; if (calc(u, v) == tr) r -= (1 << i); // cout << l << ' ' << r << '\n'; } // int ans = l; for (int i = 17; i >= 0; i--) { if (l + (1 << i) > r) continue; int j = l + (1 << i); int s = tmp[j-1], u = tmp[j], v = tmp[j+1]; if (calc(s, u) > calc(u, v)) l += (1 << i); // cout << l << ' ' << r << '\n'; } for (int i = 17; i >= 0; i--) { if (l + (1 << i) > r) continue; int j = l + (1 << i); int s = tmp[j-1], u = tmp[j], v = tmp[j+1]; if (calc(s, u) < calc(u, v)) r -= (1 << i); } int ans =INT_MAX; // cout << l << ' ' << r << '\n'; for (int i = l; i <= r; i++) ans = min(ans, calc(tmp[i], tmp[i+1])); // cerr << "ok\n"; // while (l < r) // { // cerr << l << ' ' << r << '\n'; // int m = (l + r)/2; // int t1 = calc(tmp[m-1], tmp[m]), // t2 = calc(tmp[m], tmp[m+1]); // if (t1 < t2) // r = m; // else if (t1 > t2) // l = m; // else // { // ans = m; // break; // } // } // if (ans) l = ans; cout << ans; } void solve() { int ans = INT_MAX; bfs(M[0], M[1]); int v = M[1]; while (v != -1) { tmp.push_back(v); v = trace[v]; } reverse(tmp.begin(), tmp.end()); // for (int i = 1; i < tmp.size(); i++) // e.push_back(mp(min(tmp[i-1], tmp[i]), max(tmp[i-1], tmp[i]))); T(); } } int main() { //freopen(smile"inp", "r", stdin); //freopen(smile"out", "w", stdout); cin.tie(0) -> sync_with_stdio(0); cin >> n >> M[0] >> M[1]; for (int i = 1; i < n; i++) { int u, v; cin >> u >> v; g[u].push_back(v); g[v].push_back(u); } // cin >> m; // for (int i = 0; i < m; i++) // cin >> M[i]; // if (m == 1) // SUB2::solve(); // else SUB4::solve(); return 0; }

Compilation message (stderr)

torrent.cpp: In function 'void dfs(int, int)':
torrent.cpp:31:23: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   31 |     for (int i = 0; i < tmp.size(); i++)
      |                     ~~^~~~~~~~~~~~
torrent.cpp: In function 'void SUB4::solve()':
torrent.cpp:147:13: warning: unused variable 'ans' [-Wunused-variable]
  147 |         int ans = INT_MAX;
      |             ^~~
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