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315 - Network.cpp
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315 - Network.cpp
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#include <bits/stdc++.h>
#define For(i, a, b, c) for(int i = (a); i <= (b); i += (c))
#define Rof(i, a, b, c) for(int i = (a); i >= (b); i += (c))
#define Forn(i, n) For(i, 0, (n) - 1, +1)
#define For1(i, n) For(i, 1, (n), +1)
#define Forall(i, x) for(auto i = (x).begin(); i != (x).end(); i++)
#define size(x) (int) (x).size()
#define all(x) (x).begin(), (x).end()
#define _ ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0), cout.precision(15);
#define debug(x) cout << #x": " << x << '\n';
#define fst first
#define snd second
#define pb push_back
#define lower lower_bound
#define upper upper_bound
#define ENDL '\n'
using namespace std;
typedef long long lli;
typedef unsigned long long ulli;
typedef pair<int, int> ii;
const int N = 105;
vector<int> g[N];
unordered_set<int> cutpoints;
int tin[N];
int fup[N];
bool vis[N];
int timer;
int n;
void cutpoints_dfs(int u, int pr = -1){
vis[u] = true;
tin[u] = fup[u] = ++timer;
int children = 0;
for(int v: g[u]){
if( v == pr ){
continue;
}
if( !vis[v] ){
cutpoints_dfs(v, u);
++children;
fup[u] = min(fup[u], fup[v]);
if( fup[v] >= tin[u] && pr != -1 ){
cutpoints.insert(u);
}
}else{
fup[u] = min(fup[u], tin[v]);
}
}
if( pr == -1 && children > 1 ){
cutpoints.insert(u);
}
}
void find_cutpoints(){
For1(u, n){
vis[u] = false;
tin[u] = -1;
fup[u] = -1;
}
cutpoints = unordered_set<int>();
For1(u, n){
if( !vis[u] ){
cutpoints_dfs(u);
}
}
}
int main(){ _
while( cin >> n, n != 0 ){
For1(u, n){
g[u] = vector<int>();
}
string s;
while( getline(cin, s), s != "0" ){
stringstream ss(s);
int u, v;
ss >> u;
while( ss >> v ){
g[u].pb(v);
g[v].pb(u);
}
}
find_cutpoints();
cout << size(cutpoints) << '\n';
}
return 0;
}