File size: 2,779 Bytes
1fd0050 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 | #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), pos(n+1);
for (int i = 1; i <= n; ++i) {
cin >> p[i];
pos[p[i]] = i;
}
vector<pair<int,int>> edges(n); // 1..n-1
vector<vector<pair<int,int>>> adj(n+1);
for (int i = 1; i <= n-1; ++i) {
int u,v;
cin >> u >> v;
edges[i] = {u,v};
adj[u].push_back({v,i});
adj[v].push_back({u,i});
}
// Root the tree at 1
vector<int> parent(n+1, 0), depth(n+1, 0), parentEdge(n+1, 0);
queue<int> q;
parent[1] = 0; depth[1] = 0;
q.push(1);
while (!q.empty()) {
int u = q.front(); q.pop();
for (auto [v, id] : adj[u]) {
if (v == parent[u]) continue;
parent[v] = u;
parentEdge[v] = id;
depth[v] = depth[u] + 1;
q.push(v);
}
}
vector<int> ops; ops.reserve(n*n/2 + 5);
auto apply_swap_edge = [&](int idx){
int a = edges[idx].first;
int b = edges[idx].second;
int va = p[a], vb = p[b];
swap(p[a], p[b]);
pos[va] = b;
pos[vb] = a;
};
for (int target = 1; target <= n; ++target) {
while (pos[target] != target) {
int v = pos[target];
int w = target;
vector<int> up, down;
int vv = v, ww = w;
while (depth[vv] > depth[ww]) {
up.push_back(parentEdge[vv]);
vv = parent[vv];
}
while (depth[ww] > depth[vv]) {
down.push_back(parentEdge[ww]);
ww = parent[ww];
}
while (vv != ww) {
up.push_back(parentEdge[vv]);
vv = parent[vv];
down.push_back(parentEdge[ww]);
ww = parent[ww];
}
// path is up followed by reverse(down)
for (int id : up) {
ops.push_back(id);
apply_swap_edge(id);
}
for (int i = (int)down.size()-1; i >= 0; --i) {
int id = down[i];
ops.push_back(id);
apply_swap_edge(id);
}
}
}
cout << ops.size() << "\n";
for (int id : ops) {
cout << 1 << " " << id << "\n";
}
}
return 0;
} |