Submission #1305047

#	Time	Username	Problem	Language	Result	Execution time	Memory
1305047		chithanhnguyen	Commuter Pass (JOI18_commuter_pass)	C++20	16 / 100	224 ms	20296 KiB

commuter_pass

#include <bits/stdc++.h>
using namespace std;

#define int long long
#define ull unsigned long long
#define ld long double
#define pii pair<int, int>
#define fi first
#define se second
#define __builtin_popcount __builtin_popcountll
#define all(x) (x).begin(), (x).end()
#define BIT(x, i) (((x) >> (i)) & 1)
#define MASK(x) ((1ll << (x)))

#define debug(a, l, r) for (int _i = (l); _i <= (r); ++_i) cout << (a)[_i] << ' '; cout << '\n';

const int MAXN = 1e5 + 5;
const int INF  = 1e18 + 5;
int n, m, s, t, x, y;
int dx[MAXN], dy[MAXN];
vector<pii> adj[MAXN];

void dijkstra(int source, int dist[]) {
    for (int i = 1; i <= n; ++i) dist[i] = INF;
    dist[source] = 0;
    priority_queue<pii, vector<pii>, greater<pii>> pq;
    pq.push({0, source});

    while (!pq.empty()) {
        int cost = pq.top().fi, u = pq.top().se;
        pq.pop();

        if (cost > dist[u]) continue;

        for (auto &e : adj[u]) {
            int v = e.fi, w = e.se;

            if (dist[v] > dist[u] + w) {
                dist[v] = dist[u] + w;
                pq.push({dist[v], v});
            }
        }
    }
}

int dp_dag(int start, int des) {
    vector<int> dist(n + 5, INF);
    dist[start] = 0;
    priority_queue<pii, vector<pii>, greater<pii>> pq;
    pq.push({0, start});

    while (!pq.empty()) {
        int cost = pq.top().fi, u = pq.top().se;
        pq.pop();

        if (cost > dist[u]) continue;

        for (auto &e : adj[u]) {
            int v = e.fi, w = e.se;

            if (dist[v] > dist[u] + w) {
                dist[v] = dist[u] + w;
                pq.push({dist[v], v});
            }
        }
    }

    vector<int> nodes(n + 5, 0);
    iota(begin(nodes) + 1, begin(nodes) + n + 1, 1);
    sort(begin(nodes) + 1, begin(nodes) + n + 1, [&] (int x, int y) {
        return (dist[x] < dist[y]);
    });

    // debug(dist, 1, n);
    // debug(nodes, 1, n);

    vector<vector<int>> dp(2, vector<int>(n + 5, INF));

    dp[0][start] = dx[start];
    dp[1][start] = dx[start] + dy[start];

    for (int i = 1; i <= n; ++i) {
        int u = nodes[i];
        // dp[0][u] = min(dp[0][u], dx[u]);
        // dp[1][u] = min(dp[1][u], dp[0][u] + dy[u]);
        for (auto &e : adj[u]) {
            int v = e.fi, w = e.se;
            if (dist[v] == dist[u] + w) {
                dp[0][v] = min(dp[0][v], dp[0][u]);
                dp[0][v] = min(dp[0][v], dx[v]);
                dp[1][v] = min(dp[1][v], dp[1][u]);
                dp[1][v] = min(dp[1][v], dp[0][v] + dy[v]);
            }
        }
    }

    return dp[1][des];
}

void solve() {
    cin >> n >> m;
    cin >> s >> t >> x >> y;
    for (int i = 1; i <= m; ++i) {
        int u, v, w; cin >> u >> v >> w;
        adj[u].push_back({v, w});
        adj[v].push_back({u, w});
    }

    dijkstra(x, dx);
    dijkstra(y, dy);

    cout << min(dp_dag(s, t), dp_dag(t, s));
}

signed main() {
    #ifdef NCTHANH
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    #endif
    ios_base::sync_with_stdio(0);
    cin.tie(nullptr); cout.tie(nullptr);

    solve();

    return 0;
}

• Subtask 1: 16 / 16
• Subtask 2: 0 / 15
• Subtask 3: 0 / 24
• Subtask 4: 0 / 45