Submission #44883

#	Time	Username	Problem	Language	Result	Execution time	Memory
44883		bogdan10bos	Pipes (CEOI15_pipes)	C++14	100 / 100	1370 ms	13396 KiB

pipes

#include <bits/stdc++.h>

using namespace std;

//#define FILE_IO

typedef pair<int, int> pii;

int N, M;
int h[100005], low[100005], vis[100005];
vector<int> edg[100005];

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 DFS(int nod, int fth)
{
    h[nod] = h[fth] + 1;
    low[nod] = h[nod];
    vis[nod] = 1;

    int father = 0;
    for(auto nxt: edg[nod])
    {
        if(nxt == fth)
        {
            father++;
            if(father == 1) continue;
        }

        if(vis[nxt])
        {
            low[nod] = min(low[nod], low[nxt]);
            continue;
        }

        DFS(nxt, nod);
        low[nod] = min(low[nod], low[nxt]);

        if(low[nxt] > h[nod])
            printf("%d %d\n", nod, nxt);
    }
}

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);

    int cnt = 0;
    for(int i = 1; i <= M; i++)
    {

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

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

        edg[x].push_back(y);
        edg[y].push_back(x);

        if(f[0].F(x) != f[0].F(y))  f[0].unite(x, y);
        else    f[1].unite(x, y);
    }

    for(int i = 1; i <= N; i++)
        if(!vis[i])
            DFS(i, 0);

    return 0;
}

Compilation message (stderr)

pipes.cpp: In function 'int main()':
pipes.cpp:78:9: warning: unused variable 'cnt' [-Wunused-variable]
     int cnt = 0;
         ^~~
pipes.cpp:75:10: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d", &N, &M);
     ~~~~~^~~~~~~~~~~~~~~~
pipes.cpp:83:14: 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: 10 / 10
• Subtask 5: 10 / 10
• Subtask 6: 10 / 10
• Subtask 7: 10 / 10
• Subtask 8: 10 / 10
• Subtask 9: 10 / 10
• Subtask 10: 10 / 10