Submission #1123913

#	Time	Username	Problem	Language	Result	Execution time	Memory
1123913		duyanhloveav	Aesthetic (NOI20_aesthetic)	C++20	36 / 100	2095 ms	60476 KiB

Aesthetic

#include <bits/stdc++.h>
using namespace std;

#define MASK(i) (1LL << (i))
#define BIT(x, i) (((x) >> (i)) & 1LL)

using ll = long long;

const int mxn = 9 + 1e6;
const int inf = 0x3f3f3f3f;
const ll lnf = 0x3f3f3f3f3f3f3f3f;

void _27augain(void) {
  ll n, m;
  cin >> n >> m;
  vector<vector<array<ll, 3>>> adj(n + 1);
  vector<ll> roads(m);
  vector<pair<ll, ll>> edges;
  for (ll i = 0; i < m; ++i) {
    ll u, v, w;
    cin >> u >> v >> w;
    adj[u].push_back({v, w, i});
    adj[v].push_back({u, w, i});
    roads[i] = w;
    edges.push_back({u, v});
  }
  if (m == n - 1) {
    set<ll> E;
    ll sumW = 0;
    function<bool(ll, ll)> dfs = [&](ll u, ll p) {
      if (u == n) {
        return true;
      }
      for (auto &[v, w, i] : adj[u]) {
        if (v ^ p) {
          if (dfs(v, u)) {
            E.insert(i);
            sumW += w;
            return true;
          }
        }
      }
      return false;
    };
    dfs(1, -1);
    ll res = sumW, wst = roads[m - 1];
    for (ll i = m - 1; i >= 0; --i) {
      if (E.count(i)) {
        res = max(res, sumW + wst);
      }
      wst = max(wst, roads[i]);
    }
    cout << res << "\n";
    return;
  }
  if (*max_element(begin(roads), end(roads)) == 1 && *min_element(begin(roads), end(roads)) == 1) {
    auto dij = [&](ll u) {
      vector<ll> dis(n + 1, lnf);
      priority_queue<pair<ll, ll>> pq;
      dis[u] = 0;
      pq.push({0, u});
      while (!pq.empty()) {
        auto [W, u] = pq.top();
        pq.pop();
        if (-W > dis[u]) {
          continue;
        }
        for (auto [v, w, i] : adj[u]) {
          if (dis[v] > dis[u] + w) {
            dis[v] = dis[u] + w;
            pq.push({-dis[v], v});
          }
        }
      }
      return dis;
    };
    auto _1 = dij(1), _n = dij(n);
    set<ll> s;
    map<pair<ll, ll>, ll> es;
    for (ll i = 0; i < (int) edges.size(); ++i) {
      auto [u, v] = edges[i];
      if (min(_1[u] + 1 + _n[v], _1[v] + 1 + _n[u]) == _1[n]) {
        s.insert(i);
        if (_1[u] + 1 + _n[v] == _1[n]) {
          ++es[{_1[u], _n[v]}];
        } else {
          ++es[{_1[v], _n[u]}];
        }
      }
    }
    ll res = _1[n];
    for (ll i = 0; i <= m - 2; ++i) {
      auto [u, v] = edges[i];
      if (s.count(i) && ((es[{_1[u], _n[v]}] == 1 && _1[u] + 1 + _n[v] == _1[n]) || (es[{_1[v], _1[u]}] == 1 && _1[v] + 1 + _n[u]))) {
        res = max(res, _1[n] + 1);
      }
    }
    cout << res << "\n";
    return;
  }
  auto dij = [&](ll i, ll add) {
    vector<ll> dis(n + 1, lnf);
    priority_queue<pair<ll, ll>> pq;
    pq.push({0, 1});
    dis[1] = 0;
    while (!pq.empty()) {
      auto [W, u] = pq.top();
      pq.pop();
      if (-W > dis[u]) {
        continue;
      }
      for (auto [v, w, ci] : adj[u]) {
        if (ci == i) {
          w += add;
        }
        if (dis[v] > dis[u] + w) {
          dis[v] = dis[u] + w;
          pq.push({-dis[v], v});
        }
      }
    }
    return dis;
  };
  ll res = dij(-1, 0)[n], wst = roads[m - 1];
  for (ll i = m - 1; i >= 0; --i) {
    res = max(res, dij(i, wst)[n]);
    wst = max(wst, roads[i]);
  }
  cout << res << "\n";
}

int32_t main(void) {
#define task "INCGRAPH"
  cin.tie(0)->sync_with_stdio(0);
  for (string iext : {"in", "inp"}) {
    if (fopen((task "." + iext).c_str(), "r")) {
      freopen((task "." + iext).c_str(), "r", stdin);
      freopen(task ".out", "w", stdout);
    }
  }
  int testcase = 1;
  // cin >> testcase;
  while (testcase--) _27augain();
  return 0;
}

Compilation message (stderr)

Aesthetic.cpp: In function 'int32_t main()':
Aesthetic.cpp:137:14: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  137 |       freopen((task "." + iext).c_str(), "r", stdin);
      |       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Aesthetic.cpp:138:14: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  138 |       freopen(task ".out", "w", stdout);
      |       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 8 / 8
• Subtask 3: 7 / 7
• Subtask 4: 0 / 15
• Subtask 5: 16 / 16
• Subtask 6: 0 / 22
• Subtask 7: 0 / 27