Submission #944281

#	Time	Username	Problem	Language	Result	Execution time	Memory
944281		GasmaskChan	Commuter Pass (JOI18_commuter_pass)	C++17	100 / 100	250 ms	40084 KiB

commuter_pass

#include <bits/stdc++.h>

using namespace std;
#define int long long
#define MAX 100007

int f[MAX];
vector<pair<int, int>> g[MAX];
vector<int> fu, fv, par[MAX], ng[MAX];
priority_queue<pair<int, int>, vector<pair<int, int>>, greater<pair<int, int>>> q;

bool indag[MAX];
void dfs(int u)
{
    indag[u] = true;
    for (int v : par[u])
    {
        ng[v].push_back(u);
        if (!indag[v]) dfs(v);
    }
}

vector<int> topo;
bool visited[MAX];
void toposort(int u)
{
    visited[u] = true;
    for (int v : ng[u]) if (!visited[v]) toposort(v);
    topo.push_back(u);
}

int32_t main()
{
    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);
//    freopen("test.inp", "r", stdin); freopen("test.out", "w", stdout);
    int n, m, s, t, st, ed;
    cin >> n >> m >> s >> t >> st >> ed;
    while (m--)
    {
        int u, v, w;
        cin >> u >> v >> w;
        g[u].emplace_back(v, w);
        g[v].emplace_back(u, w);
    }

    auto dij = [&](int start, vector<int> &cur) {
        cur.assign(n + 2, 1e18);
        cur[start] = 0;
        q.emplace(0, start);
        while (!q.empty())
        {
            int w, u;
            tie(w, u) = q.top();
            q.pop();

            if (cur[u] != w) continue;
            for (auto [v, c] : g[u])
                if (cur[u] + c < cur[v]) q.emplace(cur[v] = cur[u] + c, v);
        }
    };

    dij(st, fu); dij(ed, fv);

    int ans = fu[ed];

    memset(f, 0x3f, sizeof f);
    f[s] = 0;
    q.emplace(0, s);
    while (!q.empty())
    {
        int w, u;
        tie(w, u) = q.top();
        q.pop();

        if (f[u] != w) continue;
        for (auto [v, c] : g[u])
            if (f[u] + c < f[v]) par[v] = {u}, q.emplace(f[v] = f[u] + c, v);
            else if (f[u] + c == f[v]) par[v].push_back(u);
    }

    dfs(t);

    vector<vector<int>> dp(n + 2, vector<int>(2, 1e18));
    toposort(s);
    std::reverse(topo.begin(), topo.end());

    for (int i = 1; i <= n; i++)
    {
        dp[i][0] = fu[i];
        dp[i][1] = fv[i];
    }

    for (int u : topo)
        for (int v : ng[u])
        {
            dp[v][0] = min(dp[v][0], dp[u][0]);
            dp[v][1] = min(dp[v][1], dp[u][1]);
        }

    for (int i = 1; i <= n; i++) if (indag[i]) ans = min({ans, dp[i][0] + fv[i], dp[i][1] + fu[i]});

    cout << ans;
    return 0;
}

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