Submission #740644

#	Time	Username	Problem	Language	Result	Execution time	Memory
740644		stevancv	Olympic Bus (JOI20_ho_t4)	C++14	100 / 100	940 ms	3572 KiB

ho_t4

#include <bits/stdc++.h>
#define ll long long
#define ld long double
#define sp ' '
#define en '\n'
#define smin(a, b) a = min(a, b)
#define smax(a, b) a = max(a, b)
using namespace std;
const int N = 200 + 2;
const int M = 5e4 + 2;
const ll linf = 1e18;
ll dist[N][N], di[N];
vector<pair<int, int>> g[N];
int u[M], v[M], c[M], d[M], is[M], prv[N], n, m;
void Dijkstra(int x) {
    for (int i = 0; i < n; i++) di[i] = linf;
    vector<int> was(n);
    priority_queue<pair<ll, int>> pq;
    di[x] = 0;
    pq.push({0, x});
    while (!pq.empty()) {
        ll v = -pq.top().first;
        int s = pq.top().second;
        pq.pop();
        if (was[s] == 1) continue;
        was[s] = 1;
        for (auto zz : g[s]) {
            int u = zz.first; int i = zz.second;
            if (di[u] > v + c[i]) {
                di[u] = v + c[i];
                pq.push({-di[u], u});
                prv[u] = i;
            }
        }
    }
}
int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
    cin >> n >> m;
    for (int i = 0; i < n; i++) for (int j = 0; j < n; j++) if (i != j) dist[i][j] = linf;
    for (int i = 0; i < m; i++) {
        cin >> u[i] >> v[i] >> c[i] >> d[i];
        u[i] -= 1; v[i] -= 1;
        smin(dist[u[i]][v[i]],(ll) c[i]);
        g[u[i]].push_back({v[i], i});
    }
    for (int k = 0; k < n; k++) for (int i = 0; i < n; i++) for (int j = 0; j < n; j++) smin(dist[i][j], dist[i][k] + dist[k][j]);
    for (int i = 0; i < n; i++) prv[i] = -1;
    Dijkstra(0);
    for (int i = 0; i < n; i++) if (prv[i] != -1) is[prv[i]] = 1;
    for (int i = 0; i < n; i++) prv[i] = -1;
    Dijkstra(n - 1);
    for (int i = 0; i < n; i++) if (prv[i] != -1) is[prv[i]] = 1;
    ll ans = linf;
    if (dist[0][n - 1] != linf && dist[n - 1][0] != linf) ans = dist[0][n - 1] + dist[n - 1][0];
    for (int i = 0; i < m; i++) {
        if (is[i] == 0) {
            ll d1 = min(dist[0][n - 1], dist[0][v[i]] + c[i] + dist[u[i]][n - 1]);
            ll d2 = min(dist[n - 1][0], dist[n - 1][v[i]] + c[i] + dist[u[i]][0]);
            if (d1 < linf && d2 < linf) smin(ans, d1 + d2 + d[i]);
            continue;
        }
        for (int j = 0; j < n; j++) g[j].clear();
        for (int j = 0; j < m; j++) {
            if (i == j) g[v[j]].push_back({u[j], j});
            else g[u[j]].push_back({v[j], j});
        }
        ll ret = d[i];
        if (ans <= ret) continue;
        Dijkstra(0);
        ret += di[n - 1];
        if (ans <= ret) continue;
        Dijkstra(n - 1);
        if (di[0] == linf) continue;
        ret += di[0];
        smin(ans, ret);
    }
    if (ans == linf) ans = -1;
    cout << ans << en;
    return 0;
}

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