/* Problem URL: https://codeforces.com/problemset/problem/1873/H */ #include #include #include using namespace std; using namespace __gnu_pbds; template > using ordered_set = tree; #define V vector #define rmin(a, b) a = min(a, b) #define rmax(a, b) a = max(a, b) #define rep(i, lim) for (int i = 0; i < (lim); i++) #define nrep(i, s, lim) for (int i = s; i < (lim); i++) #define repv(i, v) for (auto &i : (v)) #define fillv(v) for (auto &itr_ : (v)) { cin >> itr_; } #define sortv(v) sort(v.begin(), v.end()) #define all(v) (v).begin(), (v).end() using vi = vector; using vvi = vector; using vvvi = vector; using vvvvi = vector; using ll = long long; using vl = vector; using vvl = vector; using vvvl = vector; using vvvvl = vector; template auto operator<<(ostream &os, const vector &vec)->ostream& { os << vec[0]; for (size_t i = 1; i < vec.size(); i++) { os << ' ' << vec[i]; } os << '\n'; return os; } template auto operator>>(istream &is, vector &vec)->istream& { for (auto &i : vec) { is >> i; } return is; } template auto operator<<(ostream &os, const vector> &vec)->ostream& { for (auto &i : vec) { os << i[0]; for (size_t j = 1; j < i.size(); j++) { os << ' ' << i[j]; } os << '\n'; } return os; } template auto operator>>(istream &is, vector> &vec)->istream& { for (auto &i : vec) { for (auto &j : i) { is >> j; } } return is; } const int oo = INT32_MAX >> 1; const ll OO = INT64_MAX >> 1; void pre() { } #define TEST 1 void solve() { int n, a, b; cin >> n >> a >> b; a--, b--; vi dsu(n); rep(i, n) { dsu[i] = i; } function find_p = [&](int i) { if (dsu[i] == i) { return dsu[i]; } return dsu[i] = find_p(dsu[i]); }; auto join = [&](int a, int b) { a = find_p(a); b = find_p(b); dsu[b] = a; return a == b; }; vi loop; pair edge; vvi graph(n); rep(i, n) { int u, v; cin >> u >> v; u--, v--; if (!join(u, v)) { graph[u].push_back(v); graph[v].push_back(u); continue; } edge = {u, v}; } vi depth(n, -1); vi parent(n); function dfs = [&](int i, int p) { depth[i] = depth[p] + 1; parent[i] = p; repv(j, graph[i]) { if (j == p) { continue; } dfs(j, i); } }; dfs(0, 0); int u = edge.first; int v = edge.second; if (depth[u] > depth[v]) { swap(u, v); } int diff = depth[v] - depth[u]; while (diff--) { loop.push_back(v); v = parent[v]; } while (u != v) { loop.push_back(u); loop.push_back(v); u = parent[u]; v = parent[v]; } loop.push_back(u); graph[edge.first].push_back(edge.second); graph[edge.second].push_back(edge.first); vi disa(n, oo); vi disb(n, oo); auto bfs = [&](int ini, vi &dis) { dis[ini] = 0; queue q; q.push(ini); while (!q.empty()) { auto i = q.front(); q.pop(); repv(j, graph[i]) { if (dis[j] > dis[i] + 1) { dis[j] = dis[i] + 1; q.push(j); } } } }; bfs(a, disa); bfs(b, disb); repv(i, loop) { if (disa[i] > disb[i]) { cout << "YES\n"; return; } } cout << "NO\n"; } int main() { ios::sync_with_stdio(false); cin.tie(nullptr); pre(); int t; (TEST && cin >> t) || (t = 1); while (t--) { solve(); } }