Triangle Partition

Triangle Partition

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 132768/132768 K (Java/Others)
Total Submission(s): 1107    Accepted Submission(s): 556
Special Judge

Problem Description

Chiaki has 3n points p1,p2,…,p3n. It is guaranteed that no three points are collinear.
Chiaki would like to construct n disjoint triangles where each vertex comes from the 3n points.

 

Input

There are multiple test cases. The first line of input contains an integer T, indicating the number of test cases. For each test case:
The first line contains an integer n (1≤n≤1000) -- the number of triangle to construct.
Each of the next 3n lines contains two integers xi and yi (−109≤xi,yi≤109).
It is guaranteed that the sum of all n does not exceed 10000.

 

Output

For each test case, output n lines contain three integers ai,bi,ci (1≤ai,bi,ci≤3n) each denoting the indices of points the i-th triangle use. If there are multiple solutions, you can output any of them.

 

Sample Input

1

1

1 2

2 3

3 5

 

Sample Output

1 2 3

 

Source

2018 Multi-University Training Contest 1

 

 

按ｘ排下序就可以了，然后按次序输出三个

#include <iostream>
#include <cstring>
#include <algorithm>
#define N 3005
using namespace std;
struct Node{
    int x,y;
    int in;
}node[N];

bool cmp(Node a,Node b){
    if(a.x == b.x){
        return a.y<b.y;
    }
    return a.x<b.x;
}

int main(){
    int t;
    while(cin>>t){
        while(t--){
            memset(node,0,sizeof(node));
            int n;
            cin>>n;
            for(int i=0;i<3*n;i++){
                cin>>node[i].x>>node[i].y;
                node[i].in = i+1;
            }
            sort(node,node+3*n,cmp);
            for(int i=0;i<3*n;i=i+3){
                cout<<node[i].in<<" "<<node[i+1].in<<" "<<node[i+2].in<<endl;
            }
        }
    }
    return 0;
}