File size: 3,448 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 | #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<vector<pair<int,int>>> adj(n+1);
unordered_map<long long,int> edgeId;
edgeId.reserve(2*(n-1));
edgeId.max_load_factor(0.7f);
for (int i = 1; i <= n-1; ++i) {
int u, v;
cin >> u >> v;
adj[u].push_back({v,i});
adj[v].push_back({u,i});
int a = min(u,v), b = max(u,v);
long long key = 1LL * a * (n + 1) + b;
edgeId[key] = i;
}
int LOG = 1;
while ((1<<LOG) <= n) ++LOG;
vector<int> depth(n+1, 0), parent(n+1, 0);
vector<vector<int>> up(LOG, vector<int>(n+1, 0));
// BFS to set parent and depth
queue<int> q;
parent[1] = 0;
depth[1] = 0;
q.push(1);
vector<int> vis(n+1,0);
vis[1]=1;
while(!q.empty()){
int u = q.front(); q.pop();
for(auto [v, id] : adj[u]){
if(!vis[v]){
vis[v]=1;
parent[v]=u;
depth[v]=depth[u]+1;
q.push(v);
}
}
}
for (int v = 1; v <= n; ++v) up[0][v] = parent[v] ? parent[v] : 0;
for (int k = 1; k < LOG; ++k) {
for (int v = 1; v <= n; ++v) {
int mid = up[k-1][v];
up[k][v] = mid ? up[k-1][mid] : 0;
}
}
auto lift = [&](int v, int k){
for (int i = 0; i < LOG && v; ++i) {
if (k & (1<<i)) v = up[i][v];
}
return v;
};
function<int(int,int)> lca = [&](int a, int b){
if (depth[a] < depth[b]) swap(a,b);
a = lift(a, depth[a]-depth[b]);
if (a == b) return a;
for (int k = LOG-1; k >= 0; --k) {
if (up[k][a] != up[k][b]) {
a = up[k][a];
b = up[k][b];
}
}
return parent[a];
};
vector<int> posOf(n+1);
for (int v = 1; v <= n; ++v) posOf[p[v]] = v;
vector<int> ops;
ops.reserve(n*n);
for (int val = 1; val <= n; ++val) {
while (posOf[val] != val) {
int u = posOf[val];
int v = val;
int w = lca(u, v);
int nxt;
if (u != w) {
nxt = parent[u];
} else {
int diff = depth[v] - depth[w] - 1;
int child = lift(v, diff);
nxt = child;
}
int a = min(u, nxt), b = max(u, nxt);
long long key = 1LL * a * (n + 1) + b;
int eid = edgeId[key];
// perform swap on edge (u, nxt)
int val_u = p[u];
int val_v = p[nxt];
swap(p[u], p[nxt]);
posOf[val_u] = nxt;
posOf[val_v] = u;
ops.push_back(eid);
}
}
cout << (int)ops.size() << "\n";
for (int id : ops) {
cout << 1 << " " << id << "\n";
}
}
return 0;
} |