Submission #57767

#	Time	Username	Problem	Language	Result	Execution time	Memory
57767		Crown	Duathlon (APIO18_duathlon)	C++14	10 / 100	373 ms	40624 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
#define X first
#define Y second
#define pb push_back
typedef long long ll;
typedef pair<int, int> ii;

const int maxn = 1e5+5;
const int maxm = 2e5+5;

int n, m; 

vector< ii > adj[maxn];
int U[maxm], V[maxm];
int num[maxn], low[maxn];
int now = 1;
bool instack[maxm];
stack<int> s;
int compno;
int col[maxm];

vector<int> tree[2*(maxn+maxm)];
int cnt[2*(maxn+maxm)];

void tarjan(int u, int p)
{
	num[u] = low[u] = now;
	now++;
	for(auto earn : adj[u])
	{
		int v = earn.X, id = earn.Y;
		if(!num[v])
		{
			if(!instack[id])
			{
				s.push(id);
				instack[id] = true;
			}
			tarjan(v, u);
			low[u] = min(low[u], low[v]);
			if(low[v]>= num[u])
			{
				// u is an articulation point
				compno++;
				while(!s.empty())
				{
					int x = s.top(); s.pop();
					col[x] = compno;
					if(x == id) break;
				}
			}
		}
		else if(v != p)
		{
			if(!instack[id])
			{
				s.push(id);
				instack[id] = true;
			}
			low[u] = min(low[u], num[v]);
		}
	}
}

ll res;

void dfs(int u, int p)
{
	cnt[u] = u>compno;
	for(auto v : tree[u])
	{
		if(v == p) continue;
		dfs(v, u);
		cnt[u] += cnt[v];
	}
}

void solve(int u, int p, int par_cnt)
{
	//printf("%d (%d)\n", u, par_cnt);
	if(u> compno)
	{
		ll tot = 0;
		ll sq = 0;
		for(auto v : tree[u])
		{
			if(v == p) continue;
			tot += cnt[v];
			sq += cnt[v]*cnt[v];
		}
		res += tot*tot-sq;
	}
	else
	{
		ll tot = 0;
		ll sq = 0;
		vector<int> ne;
		for(auto v : tree[u])
		{
			if(v == p) continue;
			ne.pb(cnt[v]);
			tot += cnt[v];
			sq += cnt[v]*cnt[v];
		}
		//printf("tot is %lld sq is %lld\n", tot, sq);
		if(par_cnt)
		{
			tot += par_cnt; sq += 1LL*par_cnt*par_cnt;
		}
		for(auto x : ne)
		{
			res += (tot-1)*(tot-1) - (sq - (2*x - 1) );
		}
	}
	//printf("res is now %lld\n", res);
	int tot = u> compno;
	for(auto v : tree[u])
	{
		if(v == p) continue;
		tot += cnt[v];
	}
	for(auto v : tree[u])
	{
		if(v == p) continue;
		solve(v, u, par_cnt+tot-cnt[v]);
	}
}

int main()
{
	scanf("%d %d", &n, &m);
	for(int i = 1; i<= m; i++)
	{
		int u, v; scanf("%d %d", &u, &v);
		U[i] = u; V[i] = v;
		adj[u].pb(ii(v, i));
		adj[v].pb(ii(u, i));
	}
	for(int i = 1; i<= n; i++)
	{
		if(num[i]) continue;
		tarjan(i, 0);
		if(!s.empty())
		{
			compno++;
			while(!s.empty())
			{
				int x = s.top(); s.pop();
				col[x] = compno++;
			}
		}
	}
	for(int i = 1; i<= m; i++)
	{
		int x = col[i];
		int u = U[i], v = V[i];
		tree[compno+u].pb(x);
		tree[x].pb(compno+u);
		tree[compno+v].pb(x);
		tree[x].pb(compno+v);
	}
	for(int i = 1; i<= compno+n; i++)
	{
		sort(tree[i].begin(), tree[i].end());
		tree[i].resize(unique(tree[i].begin(), tree[i].end())-tree[i].begin());
	}
	for(int i = 1; i<= compno+n; i++)
	{
		if(cnt[i]) continue;
		dfs(i, 0);
		solve(i, 0, 0);
	}
	printf("%lld\n", res);
}

Compilation message (stderr)

count_triplets.cpp: In function 'int main()':
count_triplets.cpp:132:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %d", &n, &m);
  ~~~~~^~~~~~~~~~~~~~~~~
count_triplets.cpp:135:18: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   int u, v; scanf("%d %d", &u, &v);
             ~~~~~^~~~~~~~~~~~~~~~~

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