Educational Codeforces Round 115 (Rated for Div. 2) D. Training Session

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題意：

思路：

#include<bits/stdc++.h>
#define ll long long
using namespace std;
ll vis[200010];
ll d[200010];
vector<ll>a[200010];

int main()
{
  int t;
  cin>>t;
  while(t--)
  {
    ll n;
    cin>>n;
    for(int i = 1; i <= n; i++)
    {
      ll num,leve;
      scanf("%lld%lld",&num,&leve);
      a[num].push_back(leve);
      vis[leve]++;
    }
    int cnt = 0;
    ll ans = n*(n-1)*(n-2)/6;
    for(int i = 1; i <= n; i++)
    {
      if(a[i].size())d[++cnt] = i;
    }
    ll k = 0;
    for(int i = 1; i <= cnt; i++)
    {
      k = 0;
      for(int j = 0; j < a[d[i]].size(); j++)
      {
        k += (vis[a[d[i]][j]]-1)*(a[d[i]].size()-1);
      }
      ans-=k;
    }
    printf("%lld\n",ans);
    for(int i = 1; i <= n; i++)a[i].clear(),d[i] = 0,vis[i] = 0;
  }
}