Submission #44878

#	Time	Username	Problem	Language	Result	Execution time	Memory
44878		bogdan10bos	Pipes (CEOI15_pipes)	C++14	30 / 100	2456 ms	65536 KiB

pipes

#include <bits/stdc++.h>

using namespace std;

//#define FILE_IO

typedef pair<int, int> pii;

int N, M;
int K, vis[100005], lst[100005];
vector<int> nodes, edg[100005];
vector<pii> critical;

int q[100005];

int f[2][100005];
void init(int id, int N)
{
    for(int i = 1; i <= N; i++) f[id][i] = i;
}
int F(int id, int x)
{
    if(f[id][x] == x)   return x;
    return f[id][x] = F(id, f[id][x]);
}
void unite(int id, int x, int y)
{
    if(F(id, x) == F(id, y))    return;
    f[id][F(id, y)] = F(id, x);
}

/*class UnionFind
{
public:
    int N;
    int f[100005];

    void init(int _N)
    {
        N = _N;
        for(int i = 1; i <= N; i++) f[i] = i;
    }

    int F(int x)
    {
        if(f[x] == x)   return x;
        return f[x] = F(f[x]);
    }

    void unite(int x, int y)
    {
        if(F(x) == F(y))    return;
        f[F(y)] = F(x);
    }
};
UnionFind f[2];*/

void gen()
{
    freopen("1.in", "w", stdout);

    int N = 10000;
    int M = 1e6;
    printf("%d %d\n", N, M);

    auto seed = chrono::high_resolution_clock::now().time_since_epoch().count();
    mt19937 gene(seed);
    uniform_int_distribution<int> uid(1, N);
    for(int i = 1; i <= M; i++)
    {
        int x = uid(gene);
        int y = uid(gene);
        printf("%d %d\n", x, y);
    }
    exit(0);
}

int main()
{
    //gen();
    #ifdef FILE_IO
    freopen("1.in", "r", stdin);
    freopen("1.out", "w", stdout);
    #endif

    scanf("%d%d", &N, &M);
    init(0, N), init(1, N);

    int cnt = 0;

    for(int i = 1; i <= M; i++)
    {
        /*int cnt = 0;
        for(int i = 1; i <= N; i++)
            cnt += edg[i].size();
        mx = max(mx, cnt);

        assert(critical.size() <= N);*/

        int x, y;
        scanf("%d%d", &x, &y);

        if(F(1, x) == F(1, y))  continue;

        cnt++;
        assert(cnt <= 2 * N);

        if(F(0, x) != F(0, y))
        {
            critical.push_back({x, y});
            unite(0, x, y);
            int fx = F(1, x);
            int fy = F(1, y);
            edg[fx].push_back(fy);
            edg[fy].push_back(fx);
            continue;
        }

        x = F(1, x);
        y = F(1, y);

        nodes.clear();
        nodes.push_back(x);
        nodes.push_back(y);

        K += 2;
        vis[x] = K; vis[y] = K + 1;

        int st = 1, dr = 2;
        q[1] = x;
        q[2] = y;

        while(st <= dr)
        {
            int nod = q[st];
            int id = vis[nod];
            st++;

            for(auto nxt: edg[nod])
            {
                nxt = F(1, nxt);
                if(vis[nxt] == id)  continue;
                if(vis[nxt] == (id ^ 1))
                {
                    int nd1 = nod;
                    int nd2 = nxt;
                    if(vis[nod] != K)   swap(nd1, nd2);
                    while(nd1 != x)
                    {
                        nodes.push_back(nd1);
                        nd1 = lst[nd1];
                    }
                    while(nd2 != y)
                    {
                        nodes.push_back(nd2);
                        nd2 = lst[nd2];
                    }
                    st = dr + 1;
                    break;
                }

                vis[nxt] = vis[nod];
                lst[nxt] = nod;
                q[++dr] = nxt;
            }
        }

        for(int i = 1; i < nodes.size(); i++)
        {
            unite(1, nodes[0], nodes[i]);
            for(auto x: edg[ nodes[i] ])
                if(F(1, x) != F(1, nodes[0]))
                    edg[ nodes[0] ].push_back(x);
            edg[ nodes[i] ].clear();
        }
        for(int i = 0; i < edg[ nodes[0] ].size(); i++)
        {
            if(F( 1, nodes[0] ) == F( 1, edg[ nodes[0] ][i]))
            {
                edg[ nodes[0] ].erase(edg[ nodes[0] ].begin() + i);
                i--;
            }
        }

        for(int i = 0; i < critical.size(); i++)
            if( F(1, critical[i].first) == F(1, critical[i].second) )
            {
                critical.erase(critical.begin() + i);
                i--;
            }
    }

    for(auto e: critical)
        if(F(1, e.first) != F(1, e.second))
            printf("%d %d\n", e.first, e.second);

    //cerr << mx << '\n';

    return 0;
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:168:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 1; i < nodes.size(); i++)
                        ~~^~~~~~~~~~~~~~
pipes.cpp:176:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 0; i < edg[ nodes[0] ].size(); i++)
                        ~~^~~~~~~~~~~~~~~~~~~~~~~~
pipes.cpp:185:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 0; i < critical.size(); i++)
                        ~~^~~~~~~~~~~~~~~~~
pipes.cpp: In function 'void gen()':
pipes.cpp:60:12: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result]
     freopen("1.in", "w", stdout);
     ~~~~~~~^~~~~~~~~~~~~~~~~~~~~
pipes.cpp: In function 'int main()':
pipes.cpp:86:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &N, &M);
     ~~~~~^~~~~~~~~~~~~~~~
pipes.cpp:101:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &x, &y);
         ~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 10 / 10
• Subtask 2: 10 / 10
• Subtask 3: 10 / 10
• Subtask 4: 0 / 10
• Subtask 5: 0 / 10
• Subtask 6: 0 / 10
• Subtask 7: 0 / 10
• Subtask 8: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10