#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
int n,m,disc[100001],low[100001],sz[200001],cnt,bcc_cnt;
vector<int> adj[100001],bcc[200001];
ll ans,N;
stack<int> st;
void tarjan(int x, int par) {
st.push(x);
low[x]=disc[x]=++cnt;
++N;
for (auto s : adj[x]) {
if (s==par) continue;
if (disc[s]) low[x]=min(low[x],disc[s]);
else {
tarjan(s,x);
low[x]=min(low[x],low[s]);
if (low[s]>=disc[x]) {
++bcc_cnt;
bcc[x].push_back(N+bcc_cnt);
while (!bcc[n+bcc_cnt].size() || bcc[n+bcc_cnt].top()!=s) {
bcc[N+bcc_cnt].push_back(st.top());
st.pop();
}
}
}
}
}
void dfs(int x) {
sz[x]= x>n ? 0 : 1;
for (auto s : bcc[x]) {
dfs(s);
sz[x]+=sz[s];
if (x>n) ans-=bcc[x].size()*sz[s]*(sz[s]-1);
}
if (x>n) ans-=bcc[x].size()*(N-sz[x])*(N-sz[x]-1);
}
int main() {
ios_base::sync_with_stdio(0); cin.tie(0);
cin>>n>>m;
for (int i=0; i<m; ++i) {
int a,b;
cin>>a>>b;
adj[a].push_back(b);
adj[b].push_back(a);
}
for (int i=1; i<=n; ++i) {
if (!disc[i]) {
N=0;
tarjan(i,0);
ans+=N*(N-1)*(N-2);
dfs(i);
}
}
cout<<ans;
}
Compilation message
count_triplets.cpp: In function 'void tarjan(int, int)':
count_triplets.cpp:27:65: error: 'class std::vector<int>' has no member named 'top'
27 | while (!bcc[n+bcc_cnt].size() || bcc[n+bcc_cnt].top()!=s) {
| ^~~
