Submission #59983

#	Time	Username	Problem	Language	Result	Execution time	Memory
59983		Flugan42	Duathlon (APIO18_duathlon)	C++14	31 / 100	299 ms	12320 KiB

count_triplets

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef vector<ll> vi;
typedef pair<ll,ll> ii;
typedef vector<ii> vii;
#define rep(i,a,b) for(int i = a; i < b; i++)
#define per(i,a,b) for(int i = a; i >= b; i--)
#define inf 1000000000000000000
#define sz(x) (ll)(x).size()

ll n,m,u,v,cur;
vector<vi> edges;
vi _,vis,tree,vis2,cnt;

void dfs(ll a){
  tree.push_back(a);
  rep(i,0,sz(edges[a])){
    ll b = edges[a][i];
    if (vis[b] == 0) {
      vis[b] = cur;
      dfs(b);
    }
  }
}

ll dfs2(ll a){
  vis2[a] = 1;
  if (cnt[a] != -1) return cnt[a];
  ll ans = 1;
  rep(i,0,sz(edges[a])){
    ll b = edges[a][i];
    if (vis2[b] == 0) {
      ans += dfs2(b);
    }
  }
  return cnt[a] = ans;
}

ll center(ll a){
  ll ans = 0,big = 0;
  rep(i,0,sz(edges[a])){
    ll b = edges[a][i];
    if (cnt[b] > cnt[a]) { continue; }
    ans += (sz(tree)-1-cnt[b])*cnt[b];
    big += cnt[b];
  }
  ans += big*(sz(tree)-1-big);
  return ans;
}

int main(){
  cin >> n >> m;
  edges.assign(n,_);
  rep(i,0,m){
    cin >> u >> v; u--; v--;
    edges[u].push_back(v);
    edges[v].push_back(u);
  }
  bool check = true;
  rep(i,0,n) if (sz(edges[i])>2) check = false;
  vis.assign(n,0); vis2.assign(n,0); cnt.assign(n,-1);
  cur = 1; ll res = 0;
  if (check){
    rep(i,0,n){
      if (vis[i] != 0) continue;
      tree.clear();
      vis[i] = cur; dfs(i); cur++;
      bool cyc = true; ll A = sz(tree);
      rep(j,0,A) if (sz(edges[tree[j]]) < 2) cyc = false;
      if (cyc) res += A*(A-1)*(A-2);
      else res += A*(A-1)*(A-2)/3;
    }
    cout << res << endl;
    exit(0);
  }
  rep(i,0,n){
    if (vis[i] != 0) continue;
    tree.clear();
    vis[i] = cur; dfs(i); cur++;
    dfs2(tree[0]);
    rep(j,0,sz(tree)){ res += center(tree[j]);  }
  }
  cout << res << endl;
}

• 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