Submission #136269

#	Time	Username	Problem	Language	Result	Execution time	Memory
136269		baluteshih	Duathlon (APIO18_duathlon)	C++14	100 / 100	170 ms	18808 KiB

count_triplets

#pragma GCC optimize("O3","unroll-loops")
#include <bits/stdc++.h>
#define pb push_back
using namespace std;
typedef long long ll;

vector<int> G[100005];
int low[100005],dfn[100005],avsub[100005],sub[100005],dft;
ll ans,c;
stack<int> st;
bitset<100005> vis;

void con(int u)
{
	vis[u]=1,++c;
	for(int i:G[u])
		if(!vis[i])
			con(i);
}

void dfs(int u,int f)
{
	low[u]=dfn[u]=++dft,sub[u]=1,ans+=(c-1)*(c-1),avsub[u]=1;
	st.push(u);
	for(int i:G[u])
		if(i!=f)
			if(!dfn[i])
			{
				dfs(i,u),sub[u]+=sub[i];
				if(low[i]>=dfn[u])
				{
					ll sq=0,sz=0;
					avsub[u]+=sub[i];
					for(int x=-1;x!=i;)
						x=st.top(),st.pop(),sq+=(ll)avsub[x]*avsub[x],++sz;
					ans-=sz*((c-sub[i])*(c-sub[i])+sq);
				}
				else
					low[u]=min(low[u],low[i]);
			}
			else if(dfn[u]>dfn[i])
				low[u]=min(low[u],dfn[i]);
}

int main()
{
	ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);
	int m,a,b,n;
	cin >> n >> m;
	while(m--)
		cin >> a >> b,G[a].pb(b),G[b].pb(a);
	for(int i=1;i<=n;++i)
		if(!vis[i])
			c=0,con(i),dfs(i,i);
	cout << ans << "\n";
}

Compilation message (stderr)

count_triplets.cpp: In function 'void dfs(int, int)':
count_triplets.cpp:26:5: warning: suggest explicit braces to avoid ambiguous 'else' [-Wdangling-else]
   if(i!=f)
     ^

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