Submission #831027

#	Time	Username	Problem	Language	Result	Execution time	Memory
831027		borisAngelov	Toll (BOI17_toll)	C++17	100 / 100	1500 ms	233568 KiB

toll

#include <bits/stdc++.h>

using namespace std;

const int maxn = 50005;
const int inf = 1000000007;

int n, m, q, k;

vector<pair<int, int>> g[maxn];
vector<pair<int, int>> rev[maxn];

struct query
{
    int l;
    int r;
    int id;
};

query queries[maxn];
int answer[maxn];

int dist[maxn];

void calc(int source, int l, int r)
{
    priority_queue<pair<int, int>> pq;
    pq.push(make_pair(0, source));
    dist[source] = 0;

    while (!pq.empty())
    {
        int node = pq.top().second;
        int curr = -pq.top().first;
        pq.pop();

        for (int i = 0; i < g[node].size(); ++i)
        {
            if (dist[g[node][i].first] > curr + g[node][i].second && g[node][i].first / k <= r)
            {
                dist[g[node][i].first] = curr + g[node][i].second;
                pq.push(make_pair(-dist[g[node][i].first], g[node][i].first));
            }
        }
    }

    while (!pq.empty())
    {
        pq.pop();
    }

    pq.push(make_pair(0, source));
    dist[source] = 0;

    while (!pq.empty())
    {
        int node = pq.top().second;
        int curr = -pq.top().first;
        pq.pop();

        for (int i = 0; i < rev[node].size(); ++i)
        {
            if (dist[rev[node][i].first] > curr + rev[node][i].second && rev[node][i].first / k >= l)
            {
                dist[rev[node][i].first] = curr + rev[node][i].second;
                pq.push(make_pair(-dist[rev[node][i].first], rev[node][i].first));
            }
        }
    }
}

void divide_and_conquer(int l, int r, vector<int> indexes)
{
    if (l >= r || indexes.empty())
    {
        return;
    }

    int mid = (l + r) / 2;

    vector<int> left_part;
    vector<int> right_part;

    for (int node_num = mid * k; node_num < min(n, (mid + 1) * k); ++node_num)
    {
        for (int i = 0; i < n; ++i)
        {
            dist[i] = inf;
        }

        calc(node_num, l, r);

        for (int i = 0; i < indexes.size(); ++i)
        {
            int node_l = queries[indexes[i]].l;
            int node_r = queries[indexes[i]].r;
            int query_idx = queries[indexes[i]].id;

            if (node_l / k <= mid && mid <= node_r / k)
            {
                if (dist[node_l] != inf && dist[node_r] != inf)
                {
                    answer[query_idx] = min(answer[query_idx], dist[node_l] + dist[node_r]);
                }
            }
            else if (node_l / k < mid)
            {
                left_part.push_back(indexes[i]);
            }
            else
            {
                right_part.push_back(indexes[i]);
            }
        }
    }

    divide_and_conquer(l, mid - 1, left_part);
    divide_and_conquer(mid + 1, r, right_part);
}

void fastIO()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
}

int main()
{
    fastIO();

    cin >> k >> n >> m >> q;

    for (int i = 1; i <= m; ++i)
    {
        int x, y, w;
        cin >> x >> y >> w;

        g[x].push_back(make_pair(y, w));
        rev[y].push_back(make_pair(x, w));
    }

    vector<int> indexes;

    for (int i = 1; i <= q; ++i)
    {
        cin >> queries[i].l >> queries[i].r;

        queries[i].id = i;
        indexes.push_back(i);
        answer[i] = inf;
    }

    int groups = n / k;

    divide_and_conquer(0, groups, indexes);

    for (int i = 1; i <= q; ++i)
    {
        if (answer[i] == inf)
        {
            cout << "-1\n";
        }
        else
        {
            cout << answer[i] << "\n";
        }
    }

    return 0;
}

Compilation message (stderr)

toll.cpp: In function 'void calc(int, int, int)':
toll.cpp:37:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   37 |         for (int i = 0; i < g[node].size(); ++i)
      |                         ~~^~~~~~~~~~~~~~~~
toll.cpp:61:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<std::pair<int, int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   61 |         for (int i = 0; i < rev[node].size(); ++i)
      |                         ~~^~~~~~~~~~~~~~~~~~
toll.cpp: In function 'void divide_and_conquer(int, int, std::vector<int>)':
toll.cpp:93:27: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   93 |         for (int i = 0; i < indexes.size(); ++i)
      |                         ~~^~~~~~~~~~~~~~~~

• Subtask 1: 7 / 7
• Subtask 2: 10 / 10
• Subtask 3: 8 / 8
• Subtask 4: 31 / 31
• Subtask 5: 44 / 44