Submission #1087677

#	Time	Username	Problem	Language	Result	Execution time	Memory
1087677		pmqwerty	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	230 ms	30496 KiB

commuter_pass

#include<bits/stdc++.h>
using namespace std;
const int MAXN = 2e5 + 100;
const long long INF = 1e18/3;
vector<pair<int, int>> a[MAXN];
void dijkstra(int s, vector<long long> &d){
    priority_queue<pair<long long,int>, vector<pair<long long, int>>, greater<pair<long long, int>>> pq;
    pq.push({0, s});
    d[s] = 0;
    while (!pq.empty()){
        int u = pq.top().second;
        pq.pop();
        for (auto x: a[u]){
             int v = x.first;
             if (d[v] > d[u] + x.second){
                 d[v] = d[u] + x.second;
                 pq.push({d[v], v});
             }
        }
    }
}
vector<long long> d1, d2, d3, d4;
vector<int> f[MAXN];
int n, m;
int s, t;
long long dp[MAXN][2];
int indegree[MAXN];
int u, v;
vector<int> topo;
void build(){
    queue<int> q;
    for (int u = 1; u <= n; u++){
         if (f[u].empty()) continue;
         if (!indegree[u]) q.push(u);
    }
    while (!q.empty()){
        int u = q.front();
        q.pop();
        topo.push_back(u);
        for (int v: f[u]){
             indegree[v]--;
             if (!indegree[v]) q.push(v);
        }
    }
}
pair<pair<int, int>, int> edge[MAXN];;
int main(){
    //freopen("BUS.inp", "r", stdin);
    //freopen("BUS.out", "w", stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cin >> n >> m;
    cin >> s >> t >> u >> v;
    d1.assign(n + 1, INF);
    d2.assign(n + 1, INF);
    d3.assign(n + 1, INF);
    d4.assign(n + 1, INF);
    for (int i = 1; i <= m; i++){
         int x, y, z;
         cin >> x >> y >> z;
         a[x].push_back({y, z});
         a[y].push_back({x, z});
         edge[i] = {{x, y}, z};
    }
    dijkstra(s, d1);
    dijkstra(t, d2);
    dijkstra(u, d3);
    dijkstra(v, d4);
    for (int i = 1; i <= m; i++){
         int x = edge[i].first.first;
         int y = edge[i].first.second;
         if (d1[x] + edge[i].second + d2[y] == d1[t]){
             f[x].push_back(y);
             indegree[y]++;
         }
         else if (d1[y] + edge[i].second + d2[x] == d1[t]){
             f[y].push_back(x);
             indegree[x]++;
         }
    }
    for (int i = 1; i <= n; i++){
         dp[i][0] = dp[i][1] = 1e18;
    }
    build();
    long long ans = d3[v];
//    reverse(topo.begin(), topo.end());
    for (int u: topo){
         dp[u][0] = min(dp[u][0], d3[u]);
         dp[u][1] = min(dp[u][1], d4[u]);
         ans = min(ans, dp[u][0] + d4[u]);
         ans = min(ans, dp[u][1] + d3[u]);
         for (int v: f[u]){
              dp[v][0] = min(dp[v][0], dp[u][0]);
              dp[v][1] = min(dp[v][1], dp[u][1]);
         }
    }
    cout << ans;
}

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