#include <bits/stdc++.h> #include <math.h> using namespace std; #define endl "\n" #define mp make_pair #define st first #define nd second #define pii pair<int, int> #define pb push_back #define _upgrade ios_base::sync_with_stdio(0), cout.setf(ios::fixed), cout.precision(10), cin.tie(0), cout.tie(0); #define REP(i, n) for (int i = 0; i < (n); ++i) #define FWD(i, a, b) for (int i = (a); i < (b); ++i) #define rep(i, n) for (int32_t i = 0; i < (n); ++i) #define fwd(i, a, b) for (int i = (a); i < (b); ++i) #define all(c) (c).begin(), (c).end() #define sz(X) (int)((X).size()) #define what(x) cerr << #x << " is " << x << endl; 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 a) -> decltype(a.begin(), out) { out << '{'; for (auto it = a.begin(); it != a.end(); it = next(it)) out << (it != a.begin() ? ", " : "") << *it; return out << '}'; } void dump() { cerr << "\n"; } template <class T, class... Ts> void dump(T a, Ts... x) { cerr << a << ", "; dump(x...); } #define DEBUG false #define debug(...) \ if (DEBUG) \ cerr << "[" #__VA_ARGS__ "]: ", dump(__VA_ARGS__) const int MAXN = 3000; vector<pii> adj[MAXN]; // adjacency list of graph vector<pii> edges; int licznosc[MAXN][MAXN]; vector<bool> visited(MAXN); vector<int> tin(MAXN), low(MAXN); int timer; int res = 0; int z1, z2; int m, n; void dfs(int v, int p = -1) { // debug(v); visited[v] = true; tin[v] = low[v] = timer++; for (auto P : adj[v]) { if (P.nd == z1 || P.nd == z2 || P.st == p) continue; auto to = P.st; if (visited[to]) { low[v] = min(low[v], tin[to]); } else { dfs(to, v); low[v] = min(low[v], low[to]); if (low[to] > tin[v] && licznosc[to][v] == 1) { res++; } } } } int find_bridges() { timer = 0; res = 0; visited.assign(n, false); tin.assign(n, -1); low.assign(n, -1); dfs(0); for (int i = 0; i < n; ++i) { if (!visited[i]) { // debug(m - 2); return m - 2; } } // debug(res); return res; } int find_brut() { timer = 0; res = 0; visited.assign(n, false); tin.assign(n, -1); low.assign(n, -1); dfs(0); for (int i = 0; i < n; ++i) { if (!visited[i]) { return 1; } } return 0; } int32_t main() { cin >> n >> m; long long global = 0; rep(i, m) { int a, b; cin >> a >> b; adj[--a].push_back({--b, i}); adj[b].push_back({a, i}); edges.push_back({a, b}); licznosc[a][b]++; licznosc[b][a]++; } rep(i, m) for (int j = i + 1; j < m; j++) { z1 = i, z2 = j; licznosc[edges[i].st][edges[i].nd]--; licznosc[edges[i].nd][edges[i].st]--; licznosc[edges[j].st][edges[j].nd]--; licznosc[edges[j].nd][edges[j].st]--; // debug(z1, z2); global += find_bridges(); licznosc[edges[i].st][edges[i].nd]++; licznosc[edges[i].nd][edges[i].st]++; licznosc[edges[j].st][edges[j].nd]++; licznosc[edges[j].nd][edges[j].st]++; } // int brut = 0; // rep(i, m) for (int j = i + 1; j < m; j++) for (int k = j + 1; k < m; k++) { // z1 = i, z2 = j, z3 = k; // debug(z1, z2, z3); // brut += find_brut(); // } // debug(brut); cout << global / 3 << endl; }
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 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 | #include <bits/stdc++.h> #include <math.h> using namespace std; #define endl "\n" #define mp make_pair #define st first #define nd second #define pii pair<int, int> #define pb push_back #define _upgrade ios_base::sync_with_stdio(0), cout.setf(ios::fixed), cout.precision(10), cin.tie(0), cout.tie(0); #define REP(i, n) for (int i = 0; i < (n); ++i) #define FWD(i, a, b) for (int i = (a); i < (b); ++i) #define rep(i, n) for (int32_t i = 0; i < (n); ++i) #define fwd(i, a, b) for (int i = (a); i < (b); ++i) #define all(c) (c).begin(), (c).end() #define sz(X) (int)((X).size()) #define what(x) cerr << #x << " is " << x << endl; 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 a) -> decltype(a.begin(), out) { out << '{'; for (auto it = a.begin(); it != a.end(); it = next(it)) out << (it != a.begin() ? ", " : "") << *it; return out << '}'; } void dump() { cerr << "\n"; } template <class T, class... Ts> void dump(T a, Ts... x) { cerr << a << ", "; dump(x...); } #define DEBUG false #define debug(...) \ if (DEBUG) \ cerr << "[" #__VA_ARGS__ "]: ", dump(__VA_ARGS__) const int MAXN = 3000; vector<pii> adj[MAXN]; // adjacency list of graph vector<pii> edges; int licznosc[MAXN][MAXN]; vector<bool> visited(MAXN); vector<int> tin(MAXN), low(MAXN); int timer; int res = 0; int z1, z2; int m, n; void dfs(int v, int p = -1) { // debug(v); visited[v] = true; tin[v] = low[v] = timer++; for (auto P : adj[v]) { if (P.nd == z1 || P.nd == z2 || P.st == p) continue; auto to = P.st; if (visited[to]) { low[v] = min(low[v], tin[to]); } else { dfs(to, v); low[v] = min(low[v], low[to]); if (low[to] > tin[v] && licznosc[to][v] == 1) { res++; } } } } int find_bridges() { timer = 0; res = 0; visited.assign(n, false); tin.assign(n, -1); low.assign(n, -1); dfs(0); for (int i = 0; i < n; ++i) { if (!visited[i]) { // debug(m - 2); return m - 2; } } // debug(res); return res; } int find_brut() { timer = 0; res = 0; visited.assign(n, false); tin.assign(n, -1); low.assign(n, -1); dfs(0); for (int i = 0; i < n; ++i) { if (!visited[i]) { return 1; } } return 0; } int32_t main() { cin >> n >> m; long long global = 0; rep(i, m) { int a, b; cin >> a >> b; adj[--a].push_back({--b, i}); adj[b].push_back({a, i}); edges.push_back({a, b}); licznosc[a][b]++; licznosc[b][a]++; } rep(i, m) for (int j = i + 1; j < m; j++) { z1 = i, z2 = j; licznosc[edges[i].st][edges[i].nd]--; licznosc[edges[i].nd][edges[i].st]--; licznosc[edges[j].st][edges[j].nd]--; licznosc[edges[j].nd][edges[j].st]--; // debug(z1, z2); global += find_bridges(); licznosc[edges[i].st][edges[i].nd]++; licznosc[edges[i].nd][edges[i].st]++; licznosc[edges[j].st][edges[j].nd]++; licznosc[edges[j].nd][edges[j].st]++; } // int brut = 0; // rep(i, m) for (int j = i + 1; j < m; j++) for (int k = j + 1; k < m; k++) { // z1 = i, z2 = j, z3 = k; // debug(z1, z2, z3); // brut += find_brut(); // } // debug(brut); cout << global / 3 << endl; } |