Submission #712230

#TimeUsernameProblemLanguageResultExecution timeMemory
712230Radin_Zahedi2Duathlon (APIO18_duathlon)C++17
100 / 100
203 ms30928 KiB
#include<bits/stdc++.h>
//#pragma GCC optimize("O2")
using namespace std;
using ll = long long;
using ld = long double;
#define pb push_back
#define mp make_pair
#define fi first
#define se second
#define sz(x) (int)x.size()
#define endl '\n'
const int mod = 1e9 + 7;
const int inf = 2e9 + 5;
const ll linf = 9e18 + 5;
 
 
int n, m;
const int N = 1e5 + 5;
vector<int> adj1[N];
bool mark[N];
int h[N];
int par[N];
int up[N];
 
vector<int> adj2[2 * N];
bool mark2[2 * N];
 
int block[N];
int bcnt[N];
 
int len[2 * N];
int par2[2 * N];
int total[2 * N];
 
 
int mull(int a, int b) {
	return (1ll * a * b) % mod;
}
 
void init() {
}
 
void input() {
	cin >> n >> m;
 
	for (int i = 1; i <= m; i++) {
		int u, v;
		cin >> u >> v;
//		u = i; v = i + 1;
 
		adj1[u].pb(v);
		adj1[v].pb(u);
	}
}
 
void dfshp(int u) {
	mark[u] = true;
 
	for (auto v : adj1[u]) {
		if (!mark[v]) {
			h[v] = h[u] + 1;
			par[v] = u;
			dfshp(v);
		}
	}
}
 
void dfsup(int u) {
	mark[u] = true;
 
	up[u] = h[u];
	for (auto v : adj1[u]) {
		if (!mark[v]) {
			dfsup(v);
			up[u] = min(up[u], up[v]);
		}
		else {
			up[u] = min(up[u], h[v]);
		}
	}
}
 
void dfsbd(int u) {
	mark[u] = true;
 
	for (auto v : adj1[u]) {
		if (!mark[v]) {
			if (up[v] == h[u]) {
				block[v] = v;
				bcnt[v] = 1;
			}
			else {
				block[v] = block[u];
			}
 
			dfsbd(v);
		}
	}
}
 
void dfslen(int u) {
	if (u <= n) {
		len[u] = bcnt[u];
	}
	else {
		len[u] = 1;
	}
 
	for (auto v : adj2[u]) {
		if (v != par2[u]) {
			par2[v] = u;
			dfslen(v);
			len[u] += len[v] - 1;
		}
	}
}
 
void dfstotal(int u, const int x) {
	total[u] = x;
 
	for (auto v : adj2[u]) {
		if (v != par2[u]) {
			dfstotal(v, x);
		}
	}
}
 
void solve() {
	vector<int> roots;
 
	fill(mark + 1, mark + n + 1, false);
	for (int r = 1; r <= n; r++) {
		if (!mark[r]) {
			dfshp(r);
			roots.pb(r);
		}
	}
 
	fill(mark + 1, mark + n + 1, false);
	for (auto r : roots) {
		if (!mark[r]) {
			dfsup(r);
		}
	}
 
	fill(mark + 1, mark + n + 1, false);
	for (auto r : roots) {
		if (!mark[r]) {
			dfsbd(r);
		}
	}
 
 
	for (int u = 1; u <= n; u++) {
		bcnt[block[u]]++;
	}
	bcnt[0] = 0;
 
 
	for (int u = 1; u <= n; u++) {
		bool cut = false;
		for (auto v : adj1[u]) {
			if (par[v] == u && block[v] == v) {
				cut = true;
			}
		}
 
		if (cut) {
			adj2[block[u]].pb(u + n);
			adj2[u + n].pb(block[u]);
		}
 
 
		if (block[u] == u) {
			adj2[block[u]].pb(par[u] + n);
			adj2[par[u] + n].pb(block[u]);
		}
	}
 
 
	ll ans = 0;
	for (auto r : roots) {
		dfslen(r + n);
		dfstotal(r + n, len[r + n]);
 
		ans += 1ll * len[r + n] * (len[r + n] - 1) * (len[r + n] - 2);
	}
 
	for (int u = 1; u <= n; u++) {
		if (!len[u]) {
			continue;
		}
 
		for (auto v : adj2[u]) {
			if (par2[u] != v) {
				ans -= 1ll * (bcnt[u] - 1) * len[v] * (len[v] - 1);
			}
		}
 
		ans -= 1ll * (bcnt[u] - 1) * (total[u] - len[u] + 1) * (total[u] - len[u]);
	}
 
	cout << ans;
}
 
void output() {
}
 
int main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
 
	int number_of_testcases = 1;
	//cin >> number_of_testcases;
	while (number_of_testcases--) {
		init();
 
		input();
 
		solve();
 
		output();
	}
 
	return 0;
}
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