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Submission #548395

# Submission time Handle Problem Language Result Execution time Memory
548395 2022-04-13T08:31:20 Z lorenzoferrari Islands (IOI08_islands) C++17
64 / 100
 376 ms 131072 KB 
#include <bits/stdc++.h>
#pragma GCC optimize ("O3")
using namespace std;
using LL = long long;

#define watch(x) cerr << (#x) << " is " << x << endl
#define int long long

vector<bool> vis, cycle;
vector<array<int, 2>> nxt;

LL max_path(const vector<int>& c, const vector<vector<array<int, 3>>>& adj) {
  auto find_cycle = [&](auto&& self, int v, int pid = -1) -> bool {
    if (vis[v]) return cycle[v] = true;
    vis[v] = true;
    for (auto [u, w, eid] : adj[v]) {
      if (eid == pid) continue;
      bool works = self(self, u, eid);
      if (works) {
        nxt[v] = {u, w};
        return cycle[v] ? false : cycle[v] = true;
      }
    }
    return false;
  };
  find_cycle(find_cycle, c[0]);
  auto path_in_tree = [&](auto&& self, int v, int p = -1) -> LL {
    LL ans = 0;
    for (auto [u, w, eid] : adj[v]) {
      if (u == p || cycle[u]) continue;
      ans = max(ans, w + self(self, u, v));
    }
    return ans;
  };
  int start = -1;
  for (int i : c) if (cycle[i]) start = i;
  vector<LL> fs;
  vector<LL> ds;
  {
    int v = start;
    LL len = 0;
    do {
      fs.push_back(path_in_tree(path_in_tree, v));
      ds.push_back(len);
      auto [nv, lw] = nxt[v];
      len += lw;
      v = nv;
    } while (v != start);
    ds.push_back(len);
  }
  int n = fs.size();
  for (int i = 0; i < n; ++i) fs.push_back(fs[i]);
  for (int i = 1; i < n; ++i) ds.push_back(ds.back() + ds[i] - ds[i-1]);
  LL ans = 0;
/*
maximize {fs[i] + fs[j] + ds[j] - ds[i]}, with i < j < i+n
fs[i] - ds[i] + max(fs[j] + ds[j])
*/
  LL best = -1e18;
  LL until = -1;
  for (int i = 0; i < n; ++i) {
    for (int j = until+1; j < i+n; ++j) {
      best = max(best, fs[j] + ds[j]);
      until = j;
    }
    ans = max(ans, fs[i] - ds[i] + best);
  }
  return ans;
}

int32_t main() {
#ifdef LORENZO
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
#endif
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int n; cin >> n;
  vector<vector<array<int, 3>>> adj(n);
  for (int i = 0; i < n; ++i) {
    int a; cin >> a; --a;
    int w; cin >> w;
    adj[i].push_back({a, w, i});
    adj[a].push_back({i, w, i});
  }
  vis.assign(n, false);
  vector<vector<int>> cc;
  auto dfs = [&](auto&& self, int v) -> void {
    vis[v] = true;
    cc.back().push_back(v);
    for (auto [u, _, __] : adj[v]) {
      if (!vis[u]) {
        self(self, u);
      }
    }
  };
  for (int i = 0; i < n; ++i) {
    if (!vis[i]) {
      cc.push_back(vector<int>(0));
      dfs(dfs, i);
    }
  }
  nxt.assign(n, {-1,-1});
  vis.assign(n, false);
  cycle.assign(n, false);
  LL ans = 0;
  for (auto& c : cc) {
    ans += max_path(c, adj);
    c.clear();
  }
  cout << ans << "\n";
}

Subtask #1
27.0 / 33.0

# Verdict Execution time Memory Grader output
1 Correct 1 ms 212 KB Output is correct
2 Incorrect 2 ms 340 KB Output isn't correct
3 Correct 1 ms 324 KB Output is correct
4 Correct 1 ms 212 KB Output is correct
5 Correct 1 ms 212 KB Output is correct
6 Correct 1 ms 212 KB Output is correct
7 Correct 1 ms 212 KB Output is correct
8 Correct 1 ms 212 KB Output is correct
9 Correct 1 ms 212 KB Output is correct
10 Incorrect 1 ms 340 KB Output isn't correct
11 Correct 1 ms 340 KB Output is correct

Subtask #2
3.0 / 3.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 468 KB Output is correct
2 Correct 2 ms 456 KB Output is correct

Subtask #3
4.0 / 4.0

# Verdict Execution time Memory Grader output
1 Correct 2 ms 596 KB Output is correct
2 Correct 3 ms 980 KB Output is correct

Subtask #4
0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 11 ms 2508 KB Output is correct
2 Correct 20 ms 6492 KB Output is correct
3 Incorrect 16 ms 3156 KB Output isn't correct
4 Halted 0 ms 0 KB -

Subtask #5
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 34 ms 8784 KB Output is correct
2 Correct 40 ms 14560 KB Output is correct

Subtask #6
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 101 ms 25456 KB Output is correct
2 Correct 101 ms 35204 KB Output is correct
3 Correct 121 ms 46872 KB Output is correct

Subtask #7
10.0 / 10.0

# Verdict Execution time Memory Grader output
1 Correct 161 ms 47888 KB Output is correct
2 Correct 209 ms 80212 KB Output is correct
3 Correct 272 ms 95760 KB Output is correct
4 Correct 325 ms 117256 KB Output is correct

Subtask #8
0 / 10.0

# Verdict Execution time Memory Grader output
1 Incorrect 357 ms 111480 KB Output isn't correct
2 Halted 0 ms 0 KB -

Subtask #9
0 / 10.0

# Verdict Execution time Memory Grader output
1 Runtime error 376 ms 131072 KB Execution killed with signal 9
2 Halted 0 ms 0 KB -