684.cpp

class Solution {
public:
    vector<int> findRedundantConnection(vector<vector<int>>& edges) {
        unordered_map<int, vector<int>> graph;
        for(const auto& edge: edges) {
            int u = edge[0];
            int v = edge[1];
            unordered_set<int> visited;
            if (hashPath(u, v, graph, visited)) return edge;
            graph[u].push_back(v);
            graph[v].push_back(u);
        }
        return {};
    }
private:
    bool hashPath(int curr, int goal, const unordered_map<int, vector<int>>& graph, unordered_set<int>& visited) {
        if (curr == goal) return true;
        visited.insert(curr);
        if (!graph.count(curr) || !graph.count(goal)) return false;
        for(int next: graph.at(curr)) {
            if (visited.count(next)) continue;
            if (hashPath(next, goal, graph, visited)) return true;
        }
        return false;
    }
};