Submission #203481

#	Time	Username	Problem	Language	Result	Execution time	Memory
203481		tri	Olympic Bus (JOI20_ho_t4)	C++14	5 / 100	1092 ms	3828 KiB

ho_t4

#include <bits/stdc++.h>

using namespace std;

typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;

typedef vector<int> vi;
typedef vector<ld> vd;
typedef vector<ll> vl;

#define pb push_back
#define f first
#define s second

namespace debug {
    const int DEBUG = false;

    template<class T1, class T2>
    void pr(const pair<T1, T2> &x);

    template<class T, size_t SZ>
    void pr(const array<T, SZ> &x);

    template<class T>
    void pr(const vector<T> &x);

    template<class T>
    void pr(const set<T> &x);

    template<class T1, class T2>
    void pr(const map<T1, T2> &x);

    template<class T>
    void pr(const T &x) { if (DEBUG) cout << x; }

    template<class T, class... Ts>
    void pr(const T &first, const Ts &... rest) { pr(first), pr(rest...); }

    template<class T1, class T2>
    void pr(const pair<T1, T2> &x) { pr("{", x.f, ", ", x.s, "}"); }

    template<class T>
    void prIn(const T &x) {
        pr("{");
        bool fst = 1;
        for (auto &a : x) {
            pr(fst ? "" : ", ", a), fst = 0;
        }
        pr("}");
    }

    template<class T, size_t SZ>
    void pr(const array<T, SZ> &x) { prIn(x); }

    template<class T>
    void pr(const vector<T> &x) { prIn(x); }

    template<class T>
    void pr(const set<T> &x) { prIn(x); }

    template<class T1, class T2>
    void pr(const map<T1, T2> &x) { prIn(x); }

    void ps() { pr("\n"), cout << flush; }

    template<class Arg, class... Args>
    void ps(const Arg &first, const Args &... rest) {
        pr(first, " ");
        ps(rest...);
    }
}
using namespace debug;

const int MAXV = 205;
const int MAXE = 5e4 + 10;
const ll INF = 1e15;

int V, E;

ll c[MAXE], r[MAXE];

struct graph {
    int u[MAXE], v[MAXE];

    int src;
    int sink;

    vi aL[MAXV];

    ll cost[MAXV];
    int pEdge[MAXV];

    vi sEdges;

    void dijkstra() {
        for (int i = 0; i < V; i++) {
            aL[i].clear();
        }
        for (int i = 0; i < E; i++) {
            aL[u[i]].pb(i);
        }

        fill(cost, cost + MAXV, INF);
        fill(pEdge, pEdge + MAXV, -1);
        sEdges.clear();

        priority_queue<pi, vector<pi>, greater<pi>> q;

        cost[src] = 0;
        q.push({0, src});

        while (!q.empty()) {
            pi st = q.top();
            q.pop();
            ll cC = st.f;
            int cV = st.s;

            if (cost[cV] < cC) {
                continue;
            }

            for (int aE : aL[cV]) {
                assert(u[aE] == cV);
                int aV = v[aE];

                if (cost[aV] > cC + c[aE]) {
                    cost[aV] = cC + c[aE];
                    pEdge[aV] = aE;
                    q.push({cost[aV], aV});
                }
            }
        }

        int cV = sink;
        while (cV != src) {
            if (pEdge[cV] == -1) break;
            sEdges.pb(pEdge[cV]);
            cV = u[pEdge[cV]];
        }
    }
};

graph g1;
graph g2;

bool specEdge[MAXE];

ll partAns[MAXE];

// compute cost for all reversed edges from src to sink
void computeCost() {
    g1.dijkstra();

//    ps("fin1");

    fill(specEdge, specEdge + MAXE, false);
    for (int x : g1.sEdges) {
        specEdge[x] = true;
    }

    g2 = g1; // g2 is reverse graph
    for (int i = 0; i < E; i++) {
        swap(g2.u[i], g2.v[i]);
    }
    swap(g2.src, g2.sink);

    g2.dijkstra();
    assert(g1.cost[g1.sink] == g2.cost[g2.sink]);

//    ps("fin2");

    fill(partAns, partAns + MAXE, INF);

    for (int i = 0; i < E; i++) {
        if (g1.cost[g1.v[i]] < g1.cost[g1.u[i]]) { // edge is against gradient
            partAns[i] = g1.cost[g1.v[i]] + g2.cost[g1.u[i]] + c[i];
            partAns[i] = min(partAns[i], g1.cost[g1.sink]); // don't use reverse edge
        } else {
            if (specEdge) {
                graph g3 = g1;
                swap(g3.u[i], g3.v[i]);
                g3.dijkstra();

                partAns[i] = g3.cost[g3.sink];
            } else {
                partAns[i] = g1.cost[g1.sink]; // just use the already found shortest path
            }
        }
    }
}

ll ans[MAXE];

int main() {
    cin >> V >> E;

    for (int i = 0; i < E; i++) {
        cin >> g1.u[i] >> g1.v[i] >> c[i] >> r[i];
        g1.u[i]--, g1.v[i]--;
    }

    g1.src = 0;
    g1.sink = V - 1;

    computeCost();
    for (int i = 0; i < E; i++) {
        ans[i] = partAns[i] + r[i];
    }
    ans[E] = g1.cost[g1.sink];

//    ps("half");
//    ps(partAns[1]);

    swap(g1.src, g1.sink);

    computeCost();
    for (int i = 0; i < E; i++) {
        ans[i] += partAns[i];
    }
    ans[E] += g1.cost[g1.sink];
//
//    ps("full");
//    ps(partAns[1]);

    ll fAns = INF;
    for (int i = 0; i <= E; i++) {
        fAns = min(fAns, ans[i]);
    }

    assert(fAns >= 0);

    if (fAns == INF) {
        fAns = -1;
    }
    cout << fAns << endl;
}

• Subtask 1: 5 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 21
• Subtask 4: 0 / 63