File size: 4,028 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 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 | #include <iostream>
#include <vector>
#include <numeric>
#include <algorithm>
#include <queue>
// Function to solve a single test case
void solve() {
int n;
std::cin >> n;
std::vector<int> p(n + 1);
std::vector<std::vector<int>> adj(n + 1);
for (int i = 1; i <= n; ++i) {
std::cin >> p[i];
}
std::vector<std::pair<int, int>> edge_list;
for (int i = 0; i < n - 1; ++i) {
int u, v;
std::cin >> u >> v;
adj[u].push_back(v);
adj[v].push_back(u);
edge_list.push_back({u, v});
}
// Precompute next hops for all pairs
std::vector<std::vector<int>> next_hop(n + 1, std::vector<int>(n + 1, 0));
for (int start_node = 1; start_node <= n; ++start_node) {
std::queue<int> q_bfs;
q_bfs.push(start_node);
std::vector<int> parent(n + 1, 0);
parent[start_node] = start_node; // Sentinel for root
std::vector<bool> visited(n + 1, false);
visited[start_node] = true;
while (!q_bfs.empty()) {
int u = q_bfs.front();
q_bfs.pop();
for (int v : adj[u]) {
if (!visited[v]) {
visited[v] = true;
parent[v] = u;
q_bfs.push(v);
}
}
}
for (int i = 1; i <= n; ++i) {
if (i == start_node) continue;
int curr = i;
while (parent[curr] != start_node) {
curr = parent[curr];
}
next_hop[start_node][i] = curr;
}
}
std::vector<std::vector<int>> operations;
while (true) {
bool sorted = true;
for (int i = 1; i <= n; ++i) {
if (p[i] != i) {
sorted = false;
break;
}
}
if (sorted) break;
std::vector<int> score2_edges, score1_edges;
for (int i = 0; i < n - 1; ++i) {
int u = edge_list[i].first;
int v = edge_list[i].second;
int val_u = p[u];
int val_v = p[v];
bool u_wants_v = false;
if (val_u != u) {
u_wants_v = (next_hop[u][val_u] == v);
}
bool v_wants_u = false;
if (val_v != v) {
v_wants_u = (next_hop[v][val_v] == u);
}
if (u_wants_v && v_wants_u) {
score2_edges.push_back(i + 1);
} else if (u_wants_v || v_wants_u) {
score1_edges.push_back(i + 1);
}
}
std::vector<int> current_op;
std::vector<bool> used_vertex(n + 1, false);
for (int edge_idx : score2_edges) {
int u = edge_list[edge_idx - 1].first;
int v = edge_list[edge_idx - 1].second;
if (!used_vertex[u] && !used_vertex[v]) {
current_op.push_back(edge_idx);
used_vertex[u] = true;
used_vertex[v] = true;
}
}
for (int edge_idx : score1_edges) {
int u = edge_list[edge_idx - 1].first;
int v = edge_list[edge_idx - 1].second;
if (!used_vertex[u] && !used_vertex[v]) {
current_op.push_back(edge_idx);
used_vertex[u] = true;
used_vertex[v] = true;
}
}
operations.push_back(current_op);
for (int edge_idx : current_op) {
int u = edge_list[edge_idx - 1].first;
int v = edge_list[edge_idx - 1].second;
std::swap(p[u], p[v]);
}
}
std::cout << operations.size() << "\n";
for (const auto& op : operations) {
std::cout << op.size();
for (int edge_idx : op) {
std::cout << " " << edge_idx;
}
std::cout << "\n";
}
}
int main() {
std::ios_base::sync_with_stdio(false);
std::cin.tie(NULL);
int t;
std::cin >> t;
while (t--) {
solve();
}
return 0;
} |