Submission #897064

#	Time	Username	Problem	Language	Result	Execution time	Memory
897064		duckindog	Commuter Pass (JOI18_commuter_pass)	C++14	0 / 100	2058 ms	18572 KiB

commuter_pass

// from duckindog wth depression
#include<bits/stdc++.h>

using namespace std;

#define int long long

using pii = pair<int, int>;
const int N = 1e5 + 10;
int n, m;
int s, t, u, v;
vector<pair<int, int>> ad[N];
int f[N], sv[N], trace[N];
void sktra(int x) {
  memset(f, 63, sizeof f);
  priority_queue<pii, vector<pii>, greater<pii>> q;
  q.emplace(f[x] = 0, x);
  while (q.size()) {
    int dis, u; tie(dis, u) = q.top(); q.pop();
    if (dis != f[u]) continue;
    for (auto duck : ad[u]) {
      int v, w; tie(v, w) = duck;
      if (f[v] > dis + w)
        q.emplace(f[v] = dis + w, v);
    }
  }
}
vector<int> node;
bool dd[N];
bool dfs(int a, int pre = 0, int dis = 0) {
  if (sv[a] != dis) return 0;
  if (a == t || dd[a]) return 1;
  bool ret = 0;
  for (auto duck : ad[a]) {
    int b, c; tie(b, c) = duck;
    if (dfs(b, a, dis + c)) {
      ret = 1;
      if (!dd[a]) node.push_back(a);
      dd[a] = 1;
    }
  }
  return ret;
}

int32_t main() {
  cin.tie(0)->sync_with_stdio(0);

  if (fopen("duck.inp", "r")) {
    freopen("duck.inp", "r", stdin);
    freopen("duck.out", "w", stdout);
  }
  cin >> n >> m;
  cin >> s >> t >> u >> v;

  for (int i = 1; i <= m; ++i) {
    int a, b, c; cin >> a >> b >> c;
    ad[a].push_back({b, c});
    ad[b].push_back({a, c});
  }
  if (s == u) {
    sktra(s);
    for (int i = 1; i <= n; ++i) sv[i] = f[i];
    dfs(s);
    sktra(v);
    int dv = dd[v] ? 0 : 1e14;
    for (auto x : node) dv = min(dv, f[x]);

    cout << dv << '\n';
    return 0;
  }



}

Compilation message (stderr)

commuter_pass.cpp: In function 'int32_t main()':
commuter_pass.cpp:49:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   49 |     freopen("duck.inp", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:50:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   50 |     freopen("duck.out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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