Submission #203526

#	Time	Username	Problem	Language	Result	Execution time	Memory
203526		Kevin_Zhang_TW	철인 이종 경기 (APIO18_duathlon)	C++17	8 / 100	158 ms	57460 KiB

count_triplets

#include<bits/stdc++.h>
#define pb emplace_back
using namespace std;
using ll = long long;
const int maxn = 300010;
int n, m;
vector<int> edge[maxn];
int low[maxn], st[maxn], stl, dep[maxn];
int cnt_b;
ll gsz;
vector<int> c[maxn<<1];
bool is_ap[maxn];
ll res;
int h;
#define c2(i) ((ll)(i) * ((ll)(i)-1) / 2)
#define p3(i) ((ll)(i) * ((ll)(i)-1) * ((ll)(i)-2))
vector<int> tree_edge[maxn<<1];
int sz[maxn<<1];
void dfs2(int now, int last = 0){
	sz[now] = c[now].size();
	for (int u : tree_edge[now]) if(u != last) {
		dfs2(u, now);
		sz[now] += sz[u] - (now > n);
	}
	//if (now > n) {
	//	assert(c[now].size() > 1);
	//	cout << "now " << now << ' ' << "sz " << sz[now] << ' ' << "apc " << apc << '\n';
	//	ll cur = c[now].size()-apc;
	//	res += cur * (c[now].size()-1) * (gsz-c[now].size());
	//	auto add = [&](ll a, ll b, ll all){
	//		cout << a << ' ' << b << ' ' << all-b << '\n';
	//		res += a * b * (all-b);
	//	};
	//	for (int u : tree_edge[now]) if(u != last) {
	//		add(cur, sz[u]-1, gsz);
	//	}
	//	add(c[now].size()-apc, gsz-sz[now], gsz);
	//	res += p3(cur);
	//}
	if (now > n){
		ll apc = 0;
		//cout << "now ";
		for (int u : c[now])
			apc += is_ap[u];//, cout << u << ' ';
		//cout << '\n';
		//cout << "sz " << sz[now] << '\n';
	ll ore = res;	
		auto add = [&](ll a_with_ap, ll b_with_ap, ll all) {
			//cout << a_with_ap << ' ' << b_with_ap << ' ' << all << '\n';
			//cout << (a_with_ap - apc) * (b_with_ap) * (a_with_ap - apc - 1) << '\n';
			res += (a_with_ap - apc) * (b_with_ap) * (a_with_ap - apc - 1) * 2;
			//cout << b_with_ap << ' ' << all - a_with_ap - b_with_ap + 1 << ' ' << a_with_ap - apc << '\n';
//			if (false)
//				cout  << "Y " << (b_with_ap) * (all - a_with_ap - b_with_ap + 1) * (a_with_ap - apc) << '\n';
			res += (b_with_ap) * (all - a_with_ap - b_with_ap + 1) * (a_with_ap - apc);
		};
		for (int u : tree_edge[now]) if(u != last) {
			add(c[now].size(), sz[u], gsz);
		}
		if (last)
			add(c[now].size(), gsz - sz[now]+1, gsz);
		res += p3(c[now].size());
		//res += (ll)(c[now].size()-1) * (ll)(c[now].size()-2) * apc;
		//cout << "all add " << res - ore << '\n';
	}
	else {
		auto add = [&](ll a, ll all){
			res += (a-1) * (all-a);
		};
		for (int u : tree_edge[now]) if(u != last){
			add(sz[u], gsz);
		}
		if (last)
			add(gsz - sz[now]+1, gsz);
	}
}
void cal(){
	for (int i = h;i < cnt_b;++i){
		for (int u : c[i]) if (is_ap[u]) {
			tree_edge[u].pb(i);
			tree_edge[i].pb(u);
		}
	}
	dfs2(h);
}


void dfs(int now, int last = 0){
	static int d;
	if (last == 0) {
		gsz = 0;
		h = cnt_b;
	}
	++gsz;
	low[now] = dep[now] = ++d;
	st[stl++] = now;
	int cnt_c = 0;
	for (int u : edge[now]) if (u != last) {
		if (!low[u]){
			dfs(u, now);
			++cnt_c;
			low[now] = min(low[now], low[u]);
			if (low[u] >= dep[now]){
				do {
					c[cnt_b].pb( st[--stl] );
				} while (st[stl] != u);
				c[cnt_b++].pb(now);
				is_ap[now] = true;
			}
		}
		else 
			low[now] = min(low[now], dep[u]);
	}
	if (last == 0 && cnt_c < 2)
		is_ap[now] = false;
	--d;
	if (last == 0)
		cal();
}
signed main(){
	ios_base::sync_with_stdio(0), cin.tie(0);
	cin >> n >> m;
	for ( int a, b, i = 0 ; i < m ; ++i) {
		cin >> a >> b;
		edge[a].pb(b);
		edge[b].pb(a);
	}
	cnt_b = n+1;
	for (int i = 1;i <= n;++i) if (!low[i])
		dfs(i);
	cout << res << '\n';
}

Compilation message (stderr)

count_triplets.cpp: In function 'void dfs2(int, int)':
count_triplets.cpp:47:5: warning: unused variable 'ore' [-Wunused-variable]
  ll ore = res; 
     ^~~

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 8 / 8
• Subtask 4: 0 / 10
• Subtask 5: 0 / 13
• Subtask 6: 0 / 15
• Subtask 7: 0 / 20
• Subtask 8: 0 / 8
• Subtask 9: 0 / 10