File size: 5,033 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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 | #include <iostream>
#include <vector>
#include <algorithm>
#include <queue>
using namespace std;
const int MAXN = 1005;
struct EdgeInfo {
int u, v, id;
};
int n;
int p[MAXN];
vector<pair<int, int>> adj[MAXN]; // neighbor, edge_index
vector<EdgeInfo> edges;
int next_node[MAXN][MAXN]; // next_node[u][target]
int dp[MAXN][2];
int best_child[MAXN];
int current_weights[MAXN];
vector<int> selected_edges;
void precompute_next() {
for (int start = 1; start <= n; ++start) {
// BFS to find parent pointers in tree rooted at 'start'
// next_node[u][start] will be the parent of u in this tree
// which corresponds to the first node on path from u to start
vector<int> q;
q.reserve(n);
q.push_back(start);
vector<bool> visited(n + 1, false);
visited[start] = true;
// For the root itself, next_node is 0 or undefined, we fill 0
next_node[start][start] = 0;
int head = 0;
while(head < q.size()){
int u = q[head++];
for(auto& edge : adj[u]){
int v = edge.first;
if(!visited[v]){
visited[v] = true;
// In the tree rooted at 'start', u is parent of v
// So path from v to start goes through u
next_node[v][start] = u;
q.push_back(v);
}
}
}
}
}
void dfs_dp(int u, int p_node) {
int sum_vals = 0;
for (auto& edge : adj[u]) {
int v = edge.first;
if (v == p_node) continue;
dfs_dp(v, u);
sum_vals += max(dp[v][0], dp[v][1]);
}
dp[u][0] = sum_vals;
dp[u][1] = -1e9;
for (auto& edge : adj[u]) {
int v = edge.first;
int id = edge.second;
if (v == p_node) continue;
if (current_weights[id] > 0) {
int val = sum_vals - max(dp[v][0], dp[v][1]) + dp[v][0] + current_weights[id];
if (val > dp[u][1]) {
dp[u][1] = val;
best_child[u] = v;
}
}
}
}
void reconstruct(int u, int p_node, bool matched_with_parent) {
if (matched_with_parent) {
for (auto& edge : adj[u]) {
int v = edge.first;
if (v == p_node) continue;
reconstruct(v, u, false);
}
} else {
if (dp[u][1] > dp[u][0]) {
int v = best_child[u];
int id = -1;
for(auto& edge : adj[u]){
if(edge.first == v) {
id = edge.second;
break;
}
}
selected_edges.push_back(id);
reconstruct(v, u, true);
for (auto& edge : adj[u]) {
int k = edge.first;
if (k == p_node || k == v) continue;
reconstruct(k, u, false);
}
} else {
for (auto& edge : adj[u]) {
int v = edge.first;
if (v == p_node) continue;
reconstruct(v, u, false);
}
}
}
}
void solve() {
cin >> n;
for (int i = 1; i <= n; ++i) {
cin >> p[i];
adj[i].clear();
}
edges.clear();
for (int i = 1; i < n; ++i) {
int u, v;
cin >> u >> v;
adj[u].push_back({v, i});
adj[v].push_back({u, i});
edges.push_back({u, v, i});
}
if (n > 1) precompute_next();
vector<vector<int>> ans_ops;
while (true) {
bool sorted = true;
for (int i = 1; i <= n; ++i) {
if (p[i] != i) {
sorted = false;
break;
}
}
if (sorted) break;
for (const auto& e : edges) {
int u = e.u;
int v = e.v;
int id = e.id;
int target_u = p[u];
int target_v = p[v];
bool u_wants_v = (next_node[u][target_u] == v);
bool v_wants_u = (next_node[v][target_v] == u);
if (u_wants_v && v_wants_u) current_weights[id] = 2;
else if (u_wants_v || v_wants_u) current_weights[id] = 1;
else current_weights[id] = 0;
}
dfs_dp(1, 0);
selected_edges.clear();
reconstruct(1, 0, false);
if (selected_edges.empty()) break;
ans_ops.push_back(selected_edges);
for (int id : selected_edges) {
int u = edges[id-1].u;
int v = edges[id-1].v;
swap(p[u], p[v]);
}
}
cout << ans_ops.size() << "\n";
for (const auto& ops : ans_ops) {
cout << ops.size();
for (int id : ops) {
cout << " " << id;
}
cout << "\n";
}
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(NULL);
int t;
if (cin >> t) {
while (t--) {
solve();
}
}
return 0;
} |