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#include "../util.h"
int lca(int u, int v);
#include <graph/virtualTree.cpp>
vector<int> d, par;
void dfs(int u, vector<vector<int>>& adj, int& counter) {
in[u] = counter++;
for (int v : adj[u]) if (v != par[u]) {
d[v] = d[u]+1;
par[v] = u;
dfs(v, adj, counter);
}
out[u] = counter;
}
int lca(int u, int v) {
if (d[u] < d[v]) swap(u, v);
while (d[u] > d[v]) u = par[u];
while (u != v) u = par[u], v = par[v];
return u;
}
void init(vector<vector<int>>& adj) {
int n = (int)ssize(adj);
d.assign(n, 0);
in = par = out = d;
int counter = 0;
dfs(0, adj, counter);
}
void stress_test() {
for (int tries = 0; tries < 50'000; tries++) {
int n = Random::integer<int>(1, 50);
Graph<NoData> g(n);
g.tree();
vector<vector<int>> adj(n);
g.forEdges([&](int a, int b){
adj[a].push_back(b);
adj[b].push_back(a);
});
init(adj);
vector<int> ind = Random::distinct(Random::integer(1, n+1), 0, n);
auto [idk, tree] = virtualTree(ind);
vector<pair<int, int>> edges;
for (int i=0; i<ssize(idk); i++) for (int v : tree[i]) {
edges.emplace_back(idk[i], idk[v]);
}
vector<pair<int, int>> edges2;
vector<bool> used(n);
for (int u : ind) for (int v : ind) used[lca(u, v)] = true;
auto dfs = [&](auto& self, int u, int p, int last) -> void {
if (used[u]) {
if (last != -1) edges2.emplace_back(last, u);
last = u;
}
for (int v : adj[u]) if (v != p) self(self, v, u, last);
};
dfs(dfs, 0, -1, -1);
ranges::sort(edges), ranges::sort(edges2);
if (edges != edges2) cerr << "WA edge list does not match" << FAIL;
}
cerr << "tested random 50'000 tests" << endl;
}
constexpr int N = 1'000'000;
void performance_test() {
timer t;
Graph<NoData> g(N);
g.tree();
vector<vector<int>> adj(N);
g.forEdges([&](int a, int b){
adj[a].push_back(b);
adj[b].push_back(a);
});
init(adj);
vector<int> ind = Random::distinct(N/2, 0, N);
ll hash = 0;
t.start();
auto [idk, tree] = virtualTree(ind);
hash = accumulate(begin(idk), end(idk), 0LL);
t.stop();
if (t.time > 1000) cerr << "too slow: " << t.time << FAIL;
cerr << "tested performance: " << t.time << "ms (hash: " << hash << ")" << endl;
}
int main() {
stress_test();
performance_test();
}
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