Submission #769999

#	Time	Username	Problem	Language	Result	Execution time	Memory
769999		mgl_diamond	Commuter Pass (JOI18_commuter_pass)	C++14	15 / 100	2086 ms	25072 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using ii = pair<int, int>;

#define foru(i, l, r) for(int i=(l); i<=(r); ++i)
#define ford(i, l, r) for(int i=(l); i>=(r); --i)
#define fore(x, v) for(auto &x : v)
#define all(x) (x).begin(), (x).end()
#define sz(x) (int)(x).size()
#define fi first
#define se second

void setIO(string name) {
  ios::sync_with_stdio(0);
  cin.tie(0); cout.tie(0);
  if (!name.empty()) {
    freopen((name + ".in").c_str(), "r", stdin);
    freopen((name + ".out").c_str(), "w", stdout);
  }
}

const ll LINF = 1e18;
const int N = 1e5+5;
int n, m, source[4];
ll ans(LINF), dist[4][N], dp[N][2];
vector<ii> graph[N];
vector<int> tree[N];

void dijkstra(int kth) {
  memset(dist[kth], 0x3f, sizeof(dist[kth]));
  dist[kth][source[kth]] = 0;
  priority_queue<pair<ll, int>> pq;      
  pq.push({0, source[kth]});
  while (!pq.empty()) {
    auto top = pq.top(); pq.pop();
    ll to = -top.fi;
    int u = top.se;
    if (to != dist[kth][u]) continue;
    fore(e, graph[u]) {
      ll cost = to + e.se;
      if (dist[kth][e.fi] > cost) {
        dist[kth][e.fi] = cost;
        pq.push({-cost, e.fi});
      }
    }
  }
}

void dfs(int u) {
  fore(v, tree[u]) {
    dfs(v);
    dp[u][0] = min(dp[u][0], min(dp[v][0], dist[2][v]));
    dp[u][1] = min(dp[u][1], min(dp[v][1], dist[3][v]));
  }
  if (dp[u][0] < LINF) {
    ans = min(ans, dp[u][0] + dist[3][u]);
  }
  if (dp[u][1] < LINF) {
    ans = min(ans, dp[u][1] + dist[2][u]);
  }
}

int main() {
  setIO("");

  cin >> n >> m;

  foru(i, 0, 3) {
    cin >> source[i];
  }

  foru(i, 1, m) {
    int u, v, w;
    cin >> u >> v >> w;
    graph[u].emplace_back(v, w);
    graph[v].emplace_back(u, w);
  }

  foru(i, 0, 3) {
    dijkstra(i);
  }

  foru(i, 1, n) {
    fore(e, graph[i]) {
      int j = e.fi;
      if (dist[0][i] + dist[1][j] + e.se != dist[0][source[1]]) continue;
      tree[i].push_back(j);
    }
  }

  memset(dp, 0x3f, sizeof(dp));
  dfs(source[0]);
  cout << min(dist[2][source[3]], ans);
}

Compilation message (stderr)

commuter_pass.cpp: In function 'void setIO(std::string)':
commuter_pass.cpp:18:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   18 |     freopen((name + ".in").c_str(), "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:19:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   19 |     freopen((name + ".out").c_str(), "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 0 / 16
• Subtask 2: 15 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 45