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void dfs1(vector<vector<int>>& adj, vector<int>& vis, vector<int>& st, int u) {
vis[u] = true;
for(auto& v : adj[u]) {
if(!vis[v])
dfs1(adj, vis, st, v);
}
st.push_back(u);
}
void dfs2(vector<vector<int>>& radj, vector<int>& vis, vector<int>& rep, int u, int r) {
vis[u] = true;
rep[u] = r;
for(auto& v : radj[u]) {
if(!vis[v])
dfs2(radj, vis, rep, v, r);
}
}
int airportConnections(vector<string> airports, vector<vector<string>> routes,
string startingAirport) {
unordered_map<string, int> idmp;
int id = 1, n = airports.size();
for(auto& airport : airports) idmp[airport] = id++;
vector<vector<int>> adj(n + 1), radj(n + 1);
vector<int> rep(n + 1), vis1(n + 1), vis2(n + 1), rpath(n + 1);
vector<int> st;
unordered_set<int> endPoints;
for(auto& route : routes) {
int u = idmp[route[0]], v = idmp[route[1]];
adj[u].push_back(v);
radj[v].push_back(u);
}
for(int i = 1; i <= n; i++)
if(!vis1[i])
dfs1(adj,vis1,st,i);
while(!st.empty()) {
auto u = st.back(); st.pop_back();
if(!vis2[u]) {
dfs2(radj, vis2, rep, u, u);
endPoints.insert(u);
}
}
for(int i = 1; i <= n; i++) {
for(auto& v : radj[i])
if(rep[v] != rep[i])
endPoints.erase(rep[i]);
}
endPoints.erase(rep[idmp[startingAirport]]);
return endPoints.size();
}
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