Submission #813114

#	Time	Username	Problem	Language	Result	Execution time	Memory
813114		trangtranha28	Commuter Pass (JOI18_commuter_pass)	C++14	100 / 100	317 ms	27236 KiB

commuter_pass

#include <bits/stdc++.h>
#define foru(i, l, r) for(int i=(l); i<=(r); ++i)
#define fore(x, v) for(auto &x : v)
#define fi first
#define se second
using namespace std;

const long long INF = 1e18;
const int N = 1e5 + 5;
int n, m, source[4];
long long ans(INF), dist[4][N], dp[N][2], vi[N];
vector <pair <int, int> > 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 <long long, int> > pq;      
  pq.push({0, source[kth]});
  while (!pq.empty()) {
    auto top = pq.top(); pq.pop();
    long long to = -top.fi;
    int u = top.se;
    if (to != dist[kth][u]) continue;
    fore(e, graph[u]) {
      long long cost = to + e.se;
      if (dist[kth][e.fi] > cost) {
        dist[kth][e.fi] = cost;
        pq.push({-cost, e.fi});
      }
    }
  }
}

void dfs(int u) {
  if (vi[u]) return;
  vi[u] = 1;
  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] < INF) {
    ans = min(ans, dp[u][0] + dist[3][u]);
  }
  if (dp[u][1] < INF) {
    ans = min(ans, dp[u][1] + dist[2][u]);
  }
}

int main() {
  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);
  return 0;
}

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