File size: 4,510 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 | #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> eu(n), ev(n);
vector<vector<pair<int,int>>> adj(n+1);
for (int i = 1; i <= n-1; ++i) {
int u, v;
cin >> u >> v;
eu[i] = u; ev[i] = v;
adj[u].push_back({v, i});
adj[v].push_back({u, i});
}
// Root the tree at 1 and prepare LCA
int LOG = 0;
while ((1 << LOG) <= n) ++LOG;
vector<vector<int>> up(LOG, vector<int>(n+1, 0));
vector<int> depth(n+1, 0);
vector<int> parentEdge(n+1, 0);
vector<int> parent(n+1, 0);
vector<int> vis(n+1, 0);
// BFS/DFS
stack<int> st;
st.push(1);
parent[1] = 0;
vis[1] = 1;
depth[1] = 0;
while (!st.empty()) {
int u = st.top(); st.pop();
for (auto [v, id] : adj[u]) {
if (!vis[v]) {
vis[v] = 1;
parent[v] = u;
parentEdge[v] = id;
depth[v] = depth[u] + 1;
st.push(v);
}
}
}
for (int i = 1; i <= n; ++i) up[0][i] = parent[i];
for (int k = 1; k < LOG; ++k) {
for (int i = 1; i <= n; ++i) {
up[k][i] = up[k-1][i] ? up[k-1][ up[k-1][i] ] : 0;
}
}
auto lca = [&](int a, int b) {
if (depth[a] < depth[b]) swap(a,b);
int diff = depth[a] - depth[b];
for (int k = 0; k < LOG; ++k) if (diff & (1<<k)) a = up[k][a];
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];
};
auto pathEdges = [&](int a, int b, vector<int>& out) {
out.clear();
int L = lca(a,b);
int x = a;
while (x != L) {
out.push_back(parentEdge[x]);
x = parent[x];
}
vector<int> tmp;
x = b;
while (x != L) {
tmp.push_back(parentEdge[x]);
x = parent[x];
}
for (int i = (int)tmp.size()-1; i >= 0; --i) out.push_back(tmp[i]);
};
// posOfVal
vector<int> pos(n+1, 0);
for (int i = 1; i <= n; ++i) pos[p[i]] = i;
// Active degrees and leaves
vector<int> deg(n+1, 0);
for (int i = 1; i <= n; ++i) deg[i] = (int)adj[i].size();
vector<char> active(n+1, 1);
deque<int> dq;
for (int i = 1; i <= n; ++i) if (deg[i] <= 1) dq.push_back(i);
vector<int> ops; ops.reserve(n * 100); // rough reserve
auto do_swap_edge = [&](int eid) {
int u = eu[eid], v = ev[eid];
int valU = p[u], valV = p[v];
swap(p[u], p[v]);
pos[valU] = v;
pos[valV] = u;
};
int activeCnt = n;
vector<int> epath;
while (activeCnt > 0) {
while (!dq.empty() && (!active[dq.front()] || deg[dq.front()] > 1)) dq.pop_front();
if (dq.empty()) {
// In case, pick any active node
int u = 1;
while (u <= n && !active[u]) ++u;
if (u > n) break;
dq.push_back(u);
continue;
}
int u = dq.front(); dq.pop_front();
if (!active[u]) continue;
// move value u to vertex u
if (pos[u] != u) {
pathEdges(pos[u], u, epath);
for (int eid : epath) {
ops.push_back(eid);
do_swap_edge(eid);
}
}
// remove u
active[u] = 0;
--activeCnt;
for (auto [v, id] : adj[u]) {
if (active[v]) {
deg[v]--;
if (deg[v] <= 1) dq.push_back(v);
}
}
}
// Output
cout << (int)ops.size() << "\n";
for (int eid : ops) {
cout << 1 << " " << eid << "\n";
}
}
return 0;
} |