Submission #977399

#	Time	Username	Problem	Language	Result	Execution time	Memory
977399		0x34c	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	494 ms	56464 KiB

commuter_pass

#include <bits/stdc++.h>
#define ll long long
#define pii pair<int, int>
#define piii pair<int, pii>
#define endl '\n'
#define int ll

using namespace std;

const int INF = 1e9*2e6 + 100;

struct node {
    int v, w, dw, x;
};

class Compare {
public:
    bool operator()(node &a, node &b)
    {
        if(a.w == b.w) return a.dw > b.dw;
        return a.w > b.w;
    }
};

signed main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    int N, M;
    cin >> N >> M;

    int S, T, U, V;
    cin >> S >> T >> U >> V;
    --S; --T; --U; --V;

    vector<vector<pii>> graph(N);
    for(int i = 0; i < M; i++) {
        int a, b, c;
        cin >> a >> b >> c;
        --a; --b;

        graph[a].push_back({b, c});
        graph[b].push_back({a, c});
    }


    auto dijkstra = [graph](int S, vector<int> &dist) {
        priority_queue<pii, vector<pii>, greater<pii>> pq;
        pq.push({0, S});
        dist[S] = 0;

        while(!pq.empty()) {
            int w, v;
            tie(w, v) = pq.top(); pq.pop();

            for(pii u : graph[v]) {
                if(dist[u.first] > w + u.second) {
                    dist[u.first] = w + u.second;
                    pq.push({dist[u.first], u.first});
                }
            }
        }
    };

    vector<int> distV(N, INF), distU(N, INF);
    dijkstra(V, distV); dijkstra(U, distU);

    vector<vector<pii>> dist(N, vector<pii>(1LL << 2, {INF, INF}));
    dist[S][0] = {0, 0};


    priority_queue<node, vector<node>, Compare> pq;
    pq.push({S, 0, 0, 0});

    while(!pq.empty()) {
        int v = pq.top().v, w = pq.top().w, dw = pq.top().dw, x = pq.top().x;
        pq.pop();
        

        // go to state 1
        if(!(x & 1) && (dist[v][x | 1].first > w || (dist[v][x | 1].first == w && dist[v][x | 1].second > dw + distU[v]))) {
            dist[v][x | 1] = {w, dw + distU[v]};
            pq.push({v, w, dw + distU[v], x|1});
        }

        // go to state 2
        if(!(x & 2) && (dist[v][x | 2].first > w || (dist[v][x | 2].first == w && dist[v][x | 2].second > dw + distV[v]))) {
            dist[v][x | 2] = {w, dw + distV[v]};
            pq.push({v, w, dw + distV[v], x|2});
        }

        for(pii u : graph[v]) {
            if((dist[u.first][x].first > w + u.second) || (dist[u.first][x].first == w + u.second && dist[u.first][x].second > dw)) {
                dist[u.first][x] = {w + u.second, dw};
                pq.push({u.first, w + u.second, dw, x});
            }
        }
    }

    cout << min(distV[U], dist[T][3].second) << endl;
}

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