Submission #701520

#	Time	Username	Problem	Language	Result	Execution time	Memory
701520		Abrar_Al_Samit	Duathlon (APIO18_duathlon)	C++17	8 / 100	65 ms	10228 KiB

count_triplets

#include<bits/stdc++.h>
using namespace std;

const int nax = 1e5 + 2;

vector<int>g[nax];
int n, m;
bool vis[nax];
int cr, sm;

void dfs(int v) {
  vis[v] = true;
  sm += g[v].size();
  ++cr;
  for(int u : g[v]) if(!vis[u]) {
    dfs(u);
  }
}
long long C(int n, int r) {
  long long ret = 1;
  for(int i=n-r+1; i<=n; ++i) {
    ret *= i;
  }
  for(int i=1; i<=r; ++i) {
    ret /= i;
  }
  return ret;
}
void PlayGround() {
  cin>>n>>m;
  for(int i=0; i<m; ++i) {
    int u, v;
    cin>>u>>v;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  long long ans = 0;
  for(int i=1; i<=n; ++i) if(!vis[i]) {
    cr = sm = 0;
    dfs(i);

    if(sm==cr * 2) {
      if(cr>=3) ans += C(cr, 3) * 6;
    } else {
      long long cur = 0;
      for(int i=1; i<=cr-2; ++i) {
        cur += C(cr-i, 2);
      }
      cur *= 2;
      ans += cur;
    }
  }
  cout<<ans<<'\n';
  // cerr << "Time elapsed: " << 1.0 * clock() / CLOCKS_PER_SEC << " s.\n";
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  PlayGround();
  return 0;
}

• Subtask 1: 0 / 5
• Subtask 2: 0 / 11
• Subtask 3: 8 / 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