#include<bits/stdc++.h>
using namespace std;
#define REP(i, n) for(int i = 0; i < n; i++)
#define FOR(i, a, b) for(int i = a; i <= b; i++)
#define ST first
#define ND second
ostream& operator<<(ostream &out, string str) {
for(char c : str) out << c;
return out;
}
template<class L, class R> ostream& operator<<(ostream &out, pair<L, R> p) {
return out << "(" << p.ST << ", " << p.ND << ")";
}
template<class T> auto operator<<(ostream &out, T &&x) -> decltype(x.begin(), out) {
out << '{';
for(auto &e : x)
out << e << (&e == &*--x.end() ? "" : ", ");
return out << '}';
}
template<class... Args> void dump(Args&&... args) {
((cerr << args << "; "), ...);
}
#ifdef DEBUG
# define debug(x...) cerr << "[" #x "]: ", dump(x), cerr << "\n"
#else
# define debug(...) false
#endif
template<class T> int size(T && a) { return (int) a.size(); }
using LL = long long;
using PII = pair<int, int>;
struct BiconComps {
using PII = pair<int, int>;
vector<vector<int>> graph;
vector<int> low, pre, s;
vector<array<int, 2>> edges;
BiconComps(int n) : graph(n), low(n), pre(n, -1) {}
void add_edge(int u, int v) {
int q = size(edges);
graph[u].emplace_back(q);
graph[v].emplace_back(q);
edges.push_back({u, v});
}
int get(int v, int id) {
return v ^ edges[id][0] ^ edges[id][1];
}
int t = 0;
void dfs(int v, int p) {
low[v] = pre[v] = t++;
bool par = false;
for(int e : graph[v]) {
int u = get(v, e);
if(u == p && !par) {
par = true;
continue;
}
else if(pre[u] == -1) {
dfs(u, v);
low[v] = min(low[v], low[u]);
}
else if(pre[v] > pre[u])
low[v] = min(low[v], pre[u]);
}
}
void init() { dfs(0, -1); }
};
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
int n, m;
cin >> n >> m;
vector<PII> edges(m);
REP(i, m) {
int a, b;
cin >> a >> b;
edges[i] = {a - 1, b - 1};
}
int ans = 0;
REP(i, m) REP(j, i) {
BiconComps b(n);
REP(k, m) if(k != i && k != j)
b.add_edge(edges[k].ST, edges[k].ND);
b.init();
bool connected = true;
REP(k, n)
if(b.pre[k] == -1)
connected = false;
if(!connected)
ans += m - 2;
else {
FOR(k, 1, n - 1)
ans += b.low[k] == b.pre[k];
}
}
cout << ans / 3 << "\n";
}
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 | #include<bits/stdc++.h> using namespace std; #define REP(i, n) for(int i = 0; i < n; i++) #define FOR(i, a, b) for(int i = a; i <= b; i++) #define ST first #define ND second ostream& operator<<(ostream &out, string str) { for(char c : str) out << c; return out; } template<class L, class R> ostream& operator<<(ostream &out, pair<L, R> p) { return out << "(" << p.ST << ", " << p.ND << ")"; } template<class T> auto operator<<(ostream &out, T &&x) -> decltype(x.begin(), out) { out << '{'; for(auto &e : x) out << e << (&e == &*--x.end() ? "" : ", "); return out << '}'; } template<class... Args> void dump(Args&&... args) { ((cerr << args << "; "), ...); } #ifdef DEBUG # define debug(x...) cerr << "[" #x "]: ", dump(x), cerr << "\n" #else # define debug(...) false #endif template<class T> int size(T && a) { return (int) a.size(); } using LL = long long; using PII = pair<int, int>; struct BiconComps { using PII = pair<int, int>; vector<vector<int>> graph; vector<int> low, pre, s; vector<array<int, 2>> edges; BiconComps(int n) : graph(n), low(n), pre(n, -1) {} void add_edge(int u, int v) { int q = size(edges); graph[u].emplace_back(q); graph[v].emplace_back(q); edges.push_back({u, v}); } int get(int v, int id) { return v ^ edges[id][0] ^ edges[id][1]; } int t = 0; void dfs(int v, int p) { low[v] = pre[v] = t++; bool par = false; for(int e : graph[v]) { int u = get(v, e); if(u == p && !par) { par = true; continue; } else if(pre[u] == -1) { dfs(u, v); low[v] = min(low[v], low[u]); } else if(pre[v] > pre[u]) low[v] = min(low[v], pre[u]); } } void init() { dfs(0, -1); } }; int main() { ios_base::sync_with_stdio(0); cin.tie(0); int n, m; cin >> n >> m; vector<PII> edges(m); REP(i, m) { int a, b; cin >> a >> b; edges[i] = {a - 1, b - 1}; } int ans = 0; REP(i, m) REP(j, i) { BiconComps b(n); REP(k, m) if(k != i && k != j) b.add_edge(edges[k].ST, edges[k].ND); b.init(); bool connected = true; REP(k, n) if(b.pre[k] == -1) connected = false; if(!connected) ans += m - 2; else { FOR(k, 1, n - 1) ans += b.low[k] == b.pre[k]; } } cout << ans / 3 << "\n"; } |
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