Submission #790314

#	Time	Username	Problem	Language	Result	Execution time	Memory
790314		Dan4Life	Duathlon (APIO18_duathlon)	C++17	0 / 100	731 ms	1048576 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define sz(a) (int)a.size()
#define all(a) begin(a),end(a)
using ar = array<int,2>;
const int mxN = (int)1e3+10;
int n, m, VV[mxN];
vector<int> adj[mxN];
int sub[mxN], totsq[mxN],xd=0;

void dfs(int s, int p){
	VV[s]=1; sub[s]=1; totsq[s]=0;
	for(auto u : adj[s]){
		if(u==p) continue;
		dfs(u,s); sub[s]+=sub[u];
		totsq[s]+=sub[u]*sub[u];
	}
}

void reroot(int s, int u, bool chk=1){
	totsq[s]-=sub[u]*sub[u];
	totsq[u]+=(n-sub[u])*(n-sub[u]);
	sub[s]-=sub[u]; sub[u]+=sub[s];
	if(chk) xd+=totsq[u];
}

void dfs2(int s, int p){
	for(auto u : adj[s]){
		if(u==p) continue;
		reroot(s,u);
		dfs2(u,s);
		reroot(u,s,0);
	}
}

int solve(int s){
	dfs(s,-1); xd = totsq[s]; 
	int tot = sub[s]; dfs2(s,-1); 
	return tot*(tot-1)*(tot-1)-xd;
}

int32_t main() {
	cin >> n >> m; int ans = 0;
	for(int i = 0; i < m; i++){
		int a, b; cin >> a >> b;
		adj[a].pb(b), adj[b].pb(a);
	}
	for(int i = 1; i <= n; i++)
		if(!VV[i]) ans+=solve(i);
	cout << ans << "\n";
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 0 / 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