#include <cstdio>
#include <vector>
#include <algorithm>
#include <iostream>
using namespace std;
#define f first
#define s second
const int MAXN = 2e5 + 13;
int odw[MAXN];
int low[MAXN];
int poz[MAXN];
pair<int, int> e[MAXN];
vector<int> v[MAXN];
int ile, trn = 0;
long long mos;
void DFS(int x, int oj, int lvl) {
ile++;
odw[x] = trn;
low[x] = poz[x] = lvl;
int coj = 0;
for (auto &it:v[x]) {
if (it == oj) {
coj++;
continue;
}
if (odw[it] == trn)
low[x] = min(low[x], poz[it]);
else {
DFS(it, x, lvl + 1);
low[x] = min(low[x], low[it]);
}
}
if (coj == 1 && low[x] == poz[x])
mos++;
}
int main() {
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
int n, m;
cin >> n >> m;
long long ans = 0;
long long M = m;
for (int i = 1; i <= m; i++)
cin >> e[i].f >> e[i].s;
for (int i = 1; i <= m; i++) {
for (int j = 1; j <= m; j++) {
if (i == j)
continue;
for (int l = 1; l <= m; l++) {
if (l != i && l != j) {
v[e[l].f].push_back(e[l].s);
v[e[l].s].push_back(e[l].f);
}
}
trn++;
ile = 0;
mos = 0;
DFS(1, 0, 1);
if (ile != n)
ans += M - 2;
else
ans += mos;
for (int l = 1; l <= n; l++) {
low[l] = 0;
v[l].clear();
}
}
}
cout << ans / 6;
return 0;
}
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 | #include <cstdio> #include <vector> #include <algorithm> #include <iostream> using namespace std; #define f first #define s second const int MAXN = 2e5 + 13; int odw[MAXN]; int low[MAXN]; int poz[MAXN]; pair<int, int> e[MAXN]; vector<int> v[MAXN]; int ile, trn = 0; long long mos; void DFS(int x, int oj, int lvl) { ile++; odw[x] = trn; low[x] = poz[x] = lvl; int coj = 0; for (auto &it:v[x]) { if (it == oj) { coj++; continue; } if (odw[it] == trn) low[x] = min(low[x], poz[it]); else { DFS(it, x, lvl + 1); low[x] = min(low[x], low[it]); } } if (coj == 1 && low[x] == poz[x]) mos++; } int main() { ios_base::sync_with_stdio(false); cin.tie(nullptr); int n, m; cin >> n >> m; long long ans = 0; long long M = m; for (int i = 1; i <= m; i++) cin >> e[i].f >> e[i].s; for (int i = 1; i <= m; i++) { for (int j = 1; j <= m; j++) { if (i == j) continue; for (int l = 1; l <= m; l++) { if (l != i && l != j) { v[e[l].f].push_back(e[l].s); v[e[l].s].push_back(e[l].f); } } trn++; ile = 0; mos = 0; DFS(1, 0, 1); if (ile != n) ans += M - 2; else ans += mos; for (int l = 1; l <= n; l++) { low[l] = 0; v[l].clear(); } } } cout << ans / 6; return 0; } |
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