Submission #44868

#	Time	Username	Problem	Language	Result	Execution time	Memory
44868		bogdan10bos	Pipes (CEOI15_pipes)	C++14	10 / 100	710 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;
queue<pii> q;

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];

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

    scanf("%d%d", &N, &M);
    f[0].init(N), f[1].init(N);

    for(int i = 1; i <= M; i++)
    {
        int x, y;
        scanf("%d%d", &x, &y);

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

        if(f[1].F(x) == f[1].F(y))  continue;

        x = f[1].F(x);
        y = f[1].F(y);

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

        while(!q.empty())   q.pop();
        K += 2;
        vis[x] = K; vis[y] = K + 1;
        q.push({x, K});
        q.push({y, K + 1});

        while(!q.empty())
        {
            int nod = q.front().first;
            int id = q.front().second;
            q.pop();

            for(auto nxt: edg[nod])
            {
                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];
                    }
                    while(!q.empty())   q.pop();
                    break;
                }

                vis[nxt] = vis[nod];
                lst[nxt] = nod;
            }
        }

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

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

    return 0;
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:115:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
         for(int i = 1; i < nodes.size(); i++)
                        ~~^~~~~~~~~~~~~~
pipes.cpp:48:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &N, &M);
     ~~~~~^~~~~~~~~~~~~~~~
pipes.cpp:54:14: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
         scanf("%d%d", &x, &y);
         ~~~~~^~~~~~~~~~~~~~~~

• Subtask 1: 0 / 10
• Subtask 2: 0 / 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