题意：
给出3n个点坐标，求划分出n个不相交的三角形，保证没有三点共线。
思路：
因为保证没有三点共线，所以最多有两个点有相同的x坐标。
那么根据x,y的优先级顺序从小到大排列点，每三个一组就可以保证不相交。
代码：
#include <iostream>
#include <iomanip>
#include <algorithm>
#include <cstring>
#include <cctype>
#include <cstdlib>
#include <cstdio>
#include <cmath>
#include <ctime>
#include <map>
#include <list>
#include <set>
#include <stack>
#include <queue>
#include <string>
#include <sstream>
#define pb push_back
#define X first
#define Y second
#define lch (o<<1)
#define rch (o<<1|1)
#define ALL(x) x.begin(),x.end()
#define INS(x) inserter(x,x.begin())
#define pii pair<int,int>
#define qclear(a) while(!a.empty())a.pop();
#define lowbit(x) (x&-x)
#define sd(n) scanf("%d",&n)
#define sdd(n,m) scanf("%d%d",&n,&m)
#define sddd(n,m,k) scanf("%d%d%d",&n,&m,&k)
#define mst(a,b) memset(a,b,sizeof(a))
#define cout3(x,y,z) cout<<x<<" "<<y<<" "<<z<<endl
#define cout2(x,y) cout<<x<<" "<<y<<endl
#define cout1(x) cout<<x<<endl
#define IOS std::ios::sync_with_stdio(false)
#define SRAND srand((unsigned int)(time(0)))
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int uint;
using namespace std;
const double PI=acos(-1.0);
const int INF=0x3f3f3f3f;
const ll mod=1e9+7;
const double eps=1e-8;
const int maxn=3005;
const int maxm=10005;
struct node{
int a,b;
int id;
bool operator < (const node& o)const{
if(a==o.a)return b<o.b;
return a<o.a;
}
};
int n;
int n3;
node p[maxn];
void solve() {
int t;
sd(t);
while(t--) {
sd(n);
n3=n*3;
for(int i=1;i<=n3;i++){
sdd(p[i].a,p[i].b);
p[i].id=i;
}
sort(p+1,p+n3+1);
for(int i=1;i<=n3;i+=3){
printf("%d %d %d\n",p[i].id,p[i+1].id,p[i+2].id);
}
}
return ;
}
int main() {
#ifdef LOCAL
freopen("in.txt","r",stdin);
// freopen("out.txt","w",stdout);
#else
// freopen("","r",stdin);
// freopen("","w",stdout);
#endif
solve();
return 0;
}