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| #include <bits/stdc++.h>
#define MAX_N 100001
#define ll long long
#define pll pair<ll, ll>
#define vpll vector<pll>
#define vll vector<ll>
#define vvll vector<vll>
#define vs vector<string>
#define vvs vector<vs>
#define usll unordered_set<ll>
#define all(a) begin(a), end(a)
using namespace std;
ll rep[MAX_N];
bool vis1[MAX_N], vis2[MAX_N], vis3[MAX_N], vis4[MAX_N];
vll st;
ll n;
void dfs1(ll u, vvll& adj) {
vis1[u] = true;
for(auto& v : adj[u])
if(!vis1[v])
dfs1(v, adj);
st.push_back(u);
}
void dfs2(ll u, ll r, vvll& radj) {
vis2[u] = true;
rep[u] = r;
for(auto& v : radj[u])
if(!vis2[v])
dfs2(v,r,radj);
}
void init() {
memset(vis1,0,sizeof(vis1));
memset(vis2,0,sizeof(vis2));
memset(vis3,0,sizeof(vis3));
memset(vis4,0,sizeof(vis4));
memset(rep, 0, sizeof(rep));
}
void dfs3(ll u, vvll& radj, usll& res) {
vis4[u] = true;
res.insert(u);
for(auto& v : radj[u]) {
if (!vis4[v] and rep[u] != rep[v])
dfs3(v, radj, res);
}
}
usll ts(ll id, vpll& edges, vvll& radj) {
unordered_map<ll,ll> ind;
unordered_map<ll, vll> repmp;
vvll compAdj(id);
for(ll i = 1; i < id; i++)
repmp[rep[i]].push_back(i);
for(auto& [u, v] : edges) {
if(rep[u] == rep[v]) continue;
ind[rep[v]] += 1;
compAdj[rep[u]].push_back(rep[v]);
}
queue<ll> q;
usll res;
for(auto& [r, mem]: repmp) {
if(ind[r] == 0)
q.push(r);
}
while(!q.empty()) {
auto r = q.front(); q.pop();
bool clear = true;
for(auto& mem : repmp[r]) {
if(vis3[mem]) continue;
bool add = true;
for(auto& v : radj[mem]) {
if(vis3[v]) continue;
add = false;
break;
}
if(add) vis3[mem] = true;
else clear = false;
}
if(!clear) {
for(auto& mem : repmp[r]) {
if(vis3[mem]) continue;
vis3[mem] = true;
dfs3(mem, radj, res);
}
}
for(auto& v : compAdj[r]) {
if(--ind[v] == 0)
q.push(v);
}
}
return res;
}
vs solve(vvs& dicts) {
ll id = 1;
init();
unordered_map<string, ll> idmp;
unordered_map<ll, string> ridmp;
for(auto& dict : dicts) {
for(auto& s : dict) {
if(idmp.count(s)) continue;
idmp[s] = id++;
ridmp[idmp[s]] = s;
}
}
vvll adj(id), radj(id);
vpll edges;
for(auto& dict: dicts) {
unordered_set<ll> vis;
ll v = idmp[dict[0]];
for(ll i = 1; i < dict.size(); i++) {
ll u = idmp[dict[i]];
if(vis.count(u)) continue;
vis.insert(u);
adj[u].push_back(v);
radj[v].push_back(u);
edges.push_back({u,v});
}
}
for(ll i = 1; i < id; i++) {
if(!vis1[i])
dfs1(i,adj);
}
while(!st.empty()) {
auto u = st.back(); st.pop_back();
if(!vis2[u])
dfs2(u,u,radj);
}
vs res;
for(auto& u : ts(id, edges, radj))
res.push_back(ridmp[u]);
sort(all(res));
return res;
}
vs split(string& dict) {
int i = 0;
string s = "";
vs res;
while(i < dict.length()) {
while(i < dict.length() and dict[i] != ' ')
s.push_back(dict[i++]);
i++;
res.push_back(s);
s = "";
}
return res;
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
while(true) {
cin>>n;
if(n == 0) break;
string dict;
vvs dicts(n);
getline(cin, dict);
while(n--) {
getline(cin, dict);
dicts[n] = split(dict);
}
auto res = solve(dicts);
cout<<res.size()<<'\n';
for(auto& s : res) cout<<s<<' ';cout<<'\n';
}
return 0;
}
|
