| #include <bits/stdc++.h> |
| using namespace std; |
|
|
| int main() { |
| ios::sync_with_stdio(false); |
| cin.tie(nullptr); |
| |
| int T; |
| if (!(cin >> T)) return 0; |
| while (T--) { |
| int n; |
| cin >> n; |
| vector<int> p(n + 1); |
| for (int i = 1; i <= n; ++i) cin >> p[i]; |
|
|
| vector<int> U(n), V(n); |
| vector<vector<pair<int,int>>> adj(n + 1); |
| for (int i = 1; i <= n - 1; ++i) { |
| int u, v; |
| cin >> u >> v; |
| U[i] = u; V[i] = v; |
| adj[u].push_back({v, i}); |
| adj[v].push_back({u, i}); |
| } |
|
|
| |
| vector<int> parent(n + 1, 0), depth(n + 1, 0), pedge(n + 1, 0); |
| vector<char> vis(n + 1, false); |
| vector<int> q; |
| q.push_back(1); |
| vis[1] = true; |
| parent[1] = 0; pedge[1] = 0; depth[1] = 0; |
| for (int i = 0; i < (int)q.size(); ++i) { |
| int u = q[i]; |
| for (auto [v, ei] : adj[u]) { |
| if (!vis[v]) { |
| vis[v] = true; |
| parent[v] = u; |
| pedge[v] = ei; |
| depth[v] = depth[u] + 1; |
| q.push_back(v); |
| } |
| } |
| } |
|
|
| |
| vector<int> pos(n + 1); |
| for (int u = 1; u <= n; ++u) pos[p[u]] = u; |
|
|
| |
| vector<int> deg(n + 1, 0); |
| for (int u = 1; u <= n; ++u) deg[u] = (int)adj[u].size(); |
| vector<char> inR(n + 1, true); |
| int rem = n; |
|
|
| deque<int> leaves; |
| for (int u = 1; u <= n; ++u) if (deg[u] <= 1) leaves.push_back(u); |
|
|
| vector<int> ops; |
|
|
| auto do_swap = [&](int e) { |
| int a = U[e], b = V[e]; |
| ops.push_back(e); |
| int va = p[a], vb = p[b]; |
| p[a] = vb; p[b] = va; |
| pos[va] = b; pos[vb] = a; |
| }; |
|
|
| auto move_token_along_path = [&](int start, int target) { |
| int x = start, y = target; |
| vector<int> up, down; |
| while (depth[x] > depth[y]) { up.push_back(pedge[x]); x = parent[x]; } |
| while (depth[y] > depth[x]) { down.push_back(pedge[y]); y = parent[y]; } |
| while (x != y) { |
| up.push_back(pedge[x]); x = parent[x]; |
| down.push_back(pedge[y]); y = parent[y]; |
| } |
| for (int e : up) do_swap(e); |
| for (int i = (int)down.size() - 1; i >= 0; --i) do_swap(down[i]); |
| }; |
|
|
| while (rem > 1) { |
| while (!leaves.empty() && (!inR[leaves.front()] || deg[leaves.front()] != 1)) leaves.pop_front(); |
| if (leaves.empty()) { |
| for (int u = 1; u <= n; ++u) |
| if (inR[u] && deg[u] == 1) leaves.push_back(u); |
| if (leaves.empty()) break; |
| } |
| int v = leaves.front(); leaves.pop_front(); |
| if (!inR[v] || deg[v] != 1) continue; |
|
|
| int cur = pos[v]; |
| if (cur != v) move_token_along_path(cur, v); |
|
|
| inR[v] = false; |
| --rem; |
|
|
| int neighbor = 0; |
| for (auto [to, ei] : adj[v]) if (inR[to]) { neighbor = to; break; } |
| deg[v] = 0; |
| if (neighbor) { |
| --deg[neighbor]; |
| if (deg[neighbor] == 1) leaves.push_back(neighbor); |
| } |
| } |
|
|
| cout << ops.size() << "\n"; |
| for (int e : ops) { |
| cout << 1 << " " << e << "\n"; |
| } |
| } |
|
|
| return 0; |
| } |
