Submission #367127

#	Time	Username	Problem	Language	Result	Execution time	Memory
367127		duchung	Pipes (CEOI15_pipes)	C++17	70 / 100	1293 ms	37740 KiB

pipes

#include <bits/stdc++.h>
using namespace std;

const int N = 1e5 + 5;
const int INF = 2e9;

int n , m;

vector<int> edge[N];
int low[N] , tin[N];
bool visited[N];

int timer = 0;

void dfs(int u , int p)
{
    tin[u] = ++timer;
    low[u] = INF;
    visited[u] = true;
    for (int i = 0 ; i < edge[u].size() ; ++i)
    {
        int v = edge[u][i];
        bool bridge = true;

        if (p == v) continue;
        if (i + 1 < edge[u].size() && edge[u][i + 1] == v) bridge = false;
        if (i - 1 >= 0 && edge[u][i - 1] == v) bridge = false;

        if (visited[v])
        {
            low[u] = min(low[u] , tin[v]);
        }
        else
        {
            dfs(v , u);
            if (low[v] > tin[u] && bridge)
            {
                cout << u << " " << v << "\n";
            }
            low[u] = min(low[u] , low[v]);
        }
    }
}

int parent[2*N] , level[2*N];

int find_set(int u)
{
    if (u == parent[u]) return u;
    return parent[u] = find_set(parent[u]);
}

bool same_set(int u , int v)
{
    if (find_set(u) == find_set(v)) return true;
    return false;
}

void union_set(int u , int v)
{
    int set1 = find_set(u);
    int set2 = find_set(v);

    if (set1 == set2) return;

    if (level[set1] < level[set2]) swap(set1 , set2);
    parent[set2] = set1;
    if (level[set1] == level[set2]) ++level[set1];
}

int main()
{
    // freopen(".inp","r",stdin);
    // freopen(".out","w",stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);

    cin >> n >> m;

    for (int i = 1 ; i <= 2 * n ; ++i) parent[i] = i;

    while(m--)
    {
        int u , v;
        cin >> u >> v;
        if (!same_set(u , v))
        {
            union_set(u , v);
            edge[u].push_back(v);
            edge[v].push_back(u);
        }
        else if (!same_set(u + n , v + n))
        {
            union_set(u + n , v + n);
            edge[u].push_back(v);
            edge[v].push_back(u);
        }
    }

    for (int i = 1 ; i <= n ; ++i) sort(edge[i].begin() , edge[i].end());
    // for (int i = 1 ; i <= n ; ++i) tin[i] = low[i] = -1 , visited[i] = false;

    for (int i = 1 ; i <= n ; ++i)
    {
        if (!visited[i])
        {
            dfs(i , -1);
        }
    }

    // cout << "\n";
    // for (int i = 1 ; i <= n ; ++i) cout << low[i] << " " << tin[i] << "\n";

}

Compilation message (stderr)

pipes.cpp: In function 'void dfs(int, int)':
pipes.cpp:20:24: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   20 |     for (int i = 0 ; i < edge[u].size() ; ++i)
      |                      ~~^~~~~~~~~~~~~~~~
pipes.cpp:26:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   26 |         if (i + 1 < edge[u].size() && edge[u][i + 1] == v) bridge = false;
      |             ~~~~~~^~~~~~~~~~~~~~~~

• 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: 0 / 10
• Subtask 9: 0 / 10
• Subtask 10: 0 / 10