Submission #445874

#	Time	Username	Problem	Language	Result	Execution time	Memory
445874		blue	Flood (IOI07_flood)	C++17	64 / 100	579 ms	51684 KiB

flood

#include <iostream>
#include <vector>
#include <deque>
#include <algorithm>
using namespace std;

const int maxN = 100'000;
const int maxW = 200'000;
vector<int> X(1+maxN), Y(1+maxN);
vector<int> A(1+maxW), B(1+maxW);

int N;
int W;

vector<bool> T(1+maxN, 0), L(1+maxN, 0), D(1+maxN, 0), R(1+maxN, 0);

const int maxR = 4*maxN + 4;
vector< vector<int> > R_edge(1+maxR, vector<int>(0));
vector< vector<int> > R_wt(1+maxR, vector<int>(0));

void add_R_edge(int u, int v, int w)
{
    R_edge[u].push_back(v);
    R_wt[u].push_back(w);

    R_edge[v].push_back(u);
    R_wt[v].push_back(w);
}

/*
    0   1
      P
    2   3

    4*i + 0
    4*i + 1
    4*i + 2
    4*i + 3
*/

const int TL = 0;
const int TR = 1;
const int DL = 2;
const int DR = 3;

const int INF = 1e9;

int main()
{
    cin >> N;
    for(int i = 1; i <= N; i++)
        cin >> X[i] >> Y[i];


    cin >> W;
    for(int j = 1; j <= W; j++)
    {
        cin >> A[j] >> B[j];

        if(X[ A[j] ] == X[ B[j] ])
        {
            if(Y[ A[j] ] > Y[ B[j] ])
                swap(A[j], B[j]);

            D[ A[j] ] = 1;
            T[ B[j] ] = 1;

            add_R_edge(4*A[j] + DL, 4*B[j] + TL, 0);
            add_R_edge(4*A[j] + DR, 4*B[j] + TR, 0);
        }
        else //if(Y[ A[j] ] == Y[ B[j] ])
        {
            if(X[ A[j] ] > X[ B[j] ])
                swap(A[j], B[j]);

            R[ A[j] ] = 1;
            L[ B[j] ] = 1;

            add_R_edge(4*A[j] + TR, 4*B[j] + TL, 0);
            add_R_edge(4*A[j] + DR, 4*B[j] + DL, 0);
        }
    }







    for(int i = 1; i <= N; i++)
    {
        add_R_edge(4*i + TL, 4*i + TR, T[i]);
        add_R_edge(4*i + TL, 4*i + DL, L[i]);
        add_R_edge(4*i + TR, 4*i + DR, R[i]);
        add_R_edge(4*i + DL, 4*i + DR, D[i]);
    }

    // cerr << "check\n";





    vector<int> outside_dist(1+maxR, INF);
    deque<int> tbv;

    vector<int> O(N);
    for(int i = 0; i < N; i++) O[i] = i+1;

    sort(O.begin(), O.end(), [] (int a1, int a2)
    {
        return X[a1] < X[a2];
    });


    for(int U: O)
    {
        // cerr << "U = " << U << '\n';
        if(outside_dist[4*U + TL] != INF) continue;
        outside_dist[4*U + TL] = 0;

        tbv.push_front(4*U + TL);

        while(!tbv.empty())
        {
            int u = tbv.front();
            tbv.pop_front();

            for(int e = 0; e < R_edge[u].size(); e++)
            {
                int v = R_edge[u][e];
                int w = R_wt[u][e];

                if(outside_dist[v] <= outside_dist[u] + w) continue;

                outside_dist[v] = outside_dist[u] + w;

                if(w == 0) tbv.push_front(v);
                else tbv.push_back(v);
            }
        }
    }

    // cerr << "check\n";


    vector<int> res;

    for(int j = 1; j <= W; j++)
    {
        if(X[ A[j] ] == X[ B[j] ])
        {
            if(outside_dist[4*A[j] + DL] == outside_dist[4*A[j] + DR])
            {
                res.push_back(j);
            }
        }
        else //if(Y[ A[j] ] == Y[ B[j] ])
        {
            if(outside_dist[4*A[j] + TR] == outside_dist[4*A[j] + DR])
            {
                res.push_back(j);
            }
        }
    }

    cout << res.size() << '\n';
    for(int r:res) cout << r << '\n';
}

Compilation message (stderr)

flood.cpp: In function 'int main()':
flood.cpp:129:30: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
  129 |             for(int e = 0; e < R_edge[u].size(); e++)
      |                            ~~^~~~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 3 / 3
• Subtask 5: 10 / 10
• Subtask 6: 3 / 3
• Subtask 7: 3 / 3
• Subtask 8: 3 / 3
• Subtask 9: 3 / 3
• Subtask 10: 9 / 9
• Subtask 11: 0 / 9
• Subtask 12: 0 / 9
• Subtask 13: 0 / 9
• Subtask 14: 0 / 9