Submission #203538

#	Time	Username	Problem	Language	Result	Execution time	Memory
203538		Kevin_Zhang_TW	Duathlon (APIO18_duathlon)	C++17	31 / 100	160 ms	54652 KiB

count_triplets

#include<bits/stdc++.h>
#define pb emplace_back
using namespace std;
using ll = long long;
#define int ll
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];
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];
int sz[maxn];
void dfs2(int now, int last = 0){
	sz[now] = c[now].size() + (now <= n);
	for (int u : tree_edge[now]) if(u != last) {
		dfs2(u, now);
		sz[now] += sz[u] - 1;
	}
	if (now > n){
		ll apc = 0;
		for (int u : c[now])
			apc += is_ap[u];
		auto add = [&](ll a_with_ap, ll b_with_ap, ll all) {
			//res += (a_with_ap - apc) * (b_with_ap - 1) * (a_with_ap - apc - 1) * 2;
			//res += (b_with_ap - 1) * (all - a_with_ap - b_with_ap + 1) * (a_with_ap - apc);
			res += (a_with_ap - apc) * (b_with_ap - 1) * (a_with_ap - apc - 1) * 2;
			res += (b_with_ap - 1) * (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());
	}
	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';
}

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