Submission #976663

#	Time	Username	Problem	Language	Result	Execution time	Memory
976663		phcbaka	Relay Marathon (NOI20_relaymarathon)	C++17	17 / 100	146 ms	28396 KiB

RelayMarathon

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

#define int long long
using ii = pair <int, int>;

int n, m, k;


void read()
{
    cin >> n >> m >> k;
}

struct vet
{
    bool spec[511] = {false};
    int a[511][511];
    ii dp[511][511];

    void calc()
    {
        memset(a, 0x3f3f, sizeof(a));
        for (int i = 1; i <= n; ++i) a[i][i] = 0;

        for (int i = 1; i <= m; ++i)
        {
            int u, v, L;
            cin >> u >> v >> L;
            a[u][v] = min(a[u][v], L);
            a[v][u] = min(a[v][u], L);
        }

        for (int i = 1; i <= k; ++i)
        {
            int u;
            cin >> u;
            spec[u] = 1;
        }

        for (int k = 1; k <= n; ++k)
            for (int i = 1; i <= n; ++i)
                for (int j = 1; j <= n; ++j)
                    a[i][j] = min(a[i][j], a[i][k]+a[k][j]);

        for (int i = 1; i <= n; ++i)
        {
            for (int j = 1; j <= n; ++j)
                if (spec[i] == 0 or spec[j] == 0 or i == j)
                {
                    dp[i][j] = ii(1e9, j);
                }
                else dp[i][j] = ii(a[i][j], j);

            sort (dp[i]+1, dp[i]+n+1);
        }

        int ans = LLONG_MAX;

        for (int i = 1; i <= n; ++i)
            for (int j = 1; j <= n; ++j)
                for (int t = 1; t <= min(5ll, n); ++t)
                    for (int c = 1; c <= min(5ll, n); ++c)
                        if (i != j and i != dp[i][t].second and i != dp[j][c].second
                            and j != dp[i][t].second and j != dp[j][c].second
                            and dp[i][t].second != dp[j][c].second)
                        {
                            ans = min(ans, dp[i][t].first + dp[j][c].first);
                        }

        cout << ans;
        exit(0);
    }
}Vetcan;

bool minimize(int &a, int b)
{
    if (a > b)
    {
        a = b;
        return true;
    }
    return false;
}

struct fullSub
{
    vector <ii> g[100011];
    int spec[100011];

    tuple <int, int, int> best_pair()
    {
            vector <int> d(n+1, INT_MAX);
            vector <int> head(n+1, 0);

            priority_queue <ii, vector <ii>, greater <ii>> pq;

            for (int i = 1; i <= n; ++i)
            {
                if (spec[i])
                {
                    spec[i] = i;
                    d[i] = 0;
                    pq.emplace(d[i], i);
                }
            }
        while (!pq.empty())
        {
            auto [du, u] = pq.top();
            pq.pop();

            if (d[u] != du)
                continue;

            for (auto [v, w] : g[u])
            {
                if (d[v] > d[u] + w)
                {
                    d[v] = d[u] + w;
                    head[v] = head[u];
                    pq.emplace(d[v], v);
                }
            }
        }

        int best = INT_MAX;
        int best_u = -1, best_v = -1;

        for (int u = 1; u <= n; ++u)
        {
            for (auto [v, w] : g[u])
            {
                if (d[u] != INT_MAX and d[v] != INT_MAX
                    and head[u] != head[v])
                {
                    if (minimize(best, d[u] + d[v] + w))
                    {
                        best = d[u] + d[v] + w;
                        best_u = head[u];
                        best_v = head[v];
                    }
                }
            }
        }

        return {best, best_u, best_v};
    }

    ii nearest_spec(int s)
    {
        vector <int> d(n+1, INT_MAX);
        priority_queue <ii, vector <ii>, greater <ii>> pq;

        d[s] = 0;
        pq.emplace(d[s], s);

        while (!pq.empty())
        {
            auto [du, u] = pq.top();
            pq.pop();

            if (d[u] != du)
                continue;

            if (spec[u])
            {
                return {d[u], u};
            }

            for (auto [v, w] : g[u])
            {
                if (d[v] > d[u] + w)
                {
                    d[v] = d[u] + w;
                    pq.emplace(d[v], v);
                }
            }
        }

        return ii (INT_MAX, 0); /// khong toi duoc
    }

    void readMore()
    {
        while (m--)
        {
            int u, v, w;
            cin >> u >> v >> w;
            g[u].push_back(ii (v, w));
            g[v].push_back(ii (u, w));
        }
        while (k--)
        {
            int u;
            cin >> u;
            spec[u] = 1;
        }
    }

    void calc()
    {
        readMore();

        auto [min_d, x, y] = best_pair();

        int best = INT_MAX;
        spec[x] = spec[y] = 0;

        /// a = x, b = y
        {
            auto [sec_min_d, z, t] = best_pair();
            minimize(best, min_d + sec_min_d);
        }
        /// a = x, c = y
        {
            auto [nearest_a, z] = nearest_spec(x);
            spec[z] = 0;
            auto [nearest_b, t] = nearest_spec(y);
            minimize(best, nearest_a + nearest_b);
            spec[z] = 1;
        }

        {
            auto [nearest_a, z] = nearest_spec(y);
            spec[z] = 0;
            auto [nearest_b, t] = nearest_spec(x);
            minimize(best, nearest_a + nearest_b);
            spec[z] = 1;
        }

        cout << best;
    }
}full;
signed main()
{
    cin.tie(0)->sync_with_stdio(0);

    #define task "cities"
    if (fopen(task ".inp", "r"))
    {
        freopen(task ".inp", "r", stdin);
        freopen(task ".out", "w", stdout);
    }

    read ();

    if (n <= 500)
    {
        Vetcan.calc();
    }

    full.calc();
    return 0;
}

Compilation message (stderr)

RelayMarathon.cpp: In function 'int main()':
RelayMarathon.cpp:241:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  241 |         freopen(task ".inp", "r", stdin);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
RelayMarathon.cpp:242:16: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  242 |         freopen(task ".out", "w", stdout);
      |         ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~

• Subtask 1: 5 / 5
• Subtask 2: 12 / 12
• Subtask 3: 0 / 25
• Subtask 4: 0 / 58