POI - Spies

Same thing as "Tree Matching" but on a functional graph. We can use the same greedy strategy of repeatedly matching a leaf to an adjacent vertex.

MLE:

int n, spy[MX];
bool vis[MX], used[MX];
vi adj[MX];

int sum;

void dfs(int x) {
    vis[x] = 1;
    trav(t,adj[x]) if (!vis[t]) {
        dfs(t);

OK:

int n, spy[MX], ST[MX], EN[MX], adj[MX];
bitset<MX> vis, used;

int sum;

void dfs(int _) {
    vi st{_};
    while (sz(st)) {
        int x = st.bk; vis[x] = 1;
        if (ST[x] == EN[x]) {