Bridges

int timer, n;
vector<bool> visited;
vector<int> tim, low;
vector<vector<int>> edges;
vector<pair<int, int>> bridges;

int dfs(int v, int p = -1)
{
    visited[v] = true;
    tim[v] = low[v] = timer++;
    for(int to : edges[v])
    {
        if(to == p) continue;
        if(visited[to])
            low[v] = min(low[v], tim[to]);
        else
        {
            dfs(to, v);
            low[v] = min(low[v], tim[to]);
            if(low[to] > tim[v])
                bridges.push_back({v, to});
        }
    }
}

void find_bridges()
{
    timer = 0, n = edges.size();
    tim.assign(n, -1), low.assign(n, -1), visited.assign(n, false);

    for(int v = 0; v < n; v++)
        if(!visited[v])
            dfs(v);
}