Submission #897202

#	Time	Username	Problem	Language	Result	Execution time	Memory
897202		duckindog	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	391 ms	31692 KiB

commuter_pass

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

using namespace std;

#define int long long

using pii = pair<int, int>;
using T = tuple<int, int, int>;
const int N = 1e5 + 10;
int n, m;
int s, t, U, V;
vector<pair<int, int>> ad[N];
int fs[N], ft[N];
int arr[N];
void sktra(int x) {
  memset(arr, 40, sizeof arr);
  priority_queue<pii, vector<pii>, greater<pii>> q;
  q.emplace(arr[x] = 0, x);
  while (q.size()) {
    int dis, u; tie(dis, u) = q.top(); q.pop();
    if (dis != arr[u]) continue;
    for (auto duck : ad[u]) {
      int v, w; tie(v, w) = duck;
      if (arr[v] > dis + w)
        q.emplace(arr[v] = dis + w, v);
    }
  }

}

int answer = LLONG_MAX;
int f[N][3];
void dijsktra(int x) {
  memset(f, 40, sizeof f);
  priority_queue<T, vector<T>, greater<T>> q;
  q.emplace(f[x][0] = 0, x, 0);
  while (q.size()) {
    int d, u, st; tie(d, u, st) = q.top(); q.pop();
    if (d != f[u][st]) continue;
    for (auto duck : ad[u]) {
      int v, w; tie(v, w) = duck;
      bool onway = fs[u] + w + ft[v] == fs[t];
      if (st != 1) {
        if (f[v][st] > d + w)
          q.emplace(f[v][st] = d + w, v, st);
      }

      if (st <= 1 && onway) {
        if (f[v][1] > d)
          q.emplace(f[v][1] = d, v, 1);
      }
      if (st == 1 && !onway) {
        if (f[v][2] > d + w)
          q.emplace(f[v][2] = d + w, v, 2);
      }
    }
  }
}

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});
  }

  sktra(s);
  for (int i = 1; i <= n; ++i) fs[i] = arr[i];
  sktra(t);
  for (int i = 1; i <= n; ++i) ft[i] = arr[i];

  dijsktra(U);
  answer = min({answer, f[V][0], f[V][1], f[V][2]});
  dijsktra(V);
  answer = min({answer, f[U][0], f[U][1], f[U][2]});

  cout << answer << '\n';
}

Compilation message (stderr)

commuter_pass.cpp: In function 'int32_t main()':
commuter_pass.cpp:65:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   65 |     freopen("duck.inp", "r", stdin);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
commuter_pass.cpp:66:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
   66 |     freopen("duck.out", "w", stdout);
      |     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

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