2019 cattle off more training school third H.Magic Line (thinking)

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Roughly meaning of the questions:

The number of test input T, the number of inputs n (n is an even number), then the coordinates are inputted n different points, required output four integers x1, y1, x2, y2, expressed through a point (x1 , y1), (x2, y2) of the points in the straight two-dimensional plane into equal portions two points. (This line can not pass through the plane at any point)

sample input：

1
4
0 1
-1 0
1 0
0 -1

sample output：（special judge）

-1 999000000 1 -999000001

answer:

In these n points x and y is the second key to the first key in ascending order, find the middle two points a and b, as a dividing line to the two points, one can always find a and b by steep linear points may be points in the plane into two parts of equal number of points.

If the sorted intermediate a, the x-coordinate of the points a and b are not the same, just one is drawn in a, a straight line between the points a and b are; intermediate sorted if a, as the x-coordinate of the points a and b, it must pass a, b midpoint straight down.

Code：

 1 #include<bits/stdc++.h>
 2 #define IO ios::sync_with_stdio(false);
 3 using namespace std;
 4 const int m=99990000;
 5 struct point
 6 {
 7     int x,y;
 8 }p[1005];
 9 bool cmp(point s1,point s2)
10 {
11     if(s1.x==s2.x)return s1.y<s2.y;
12     else return s1.x<s2.x;
13 }
14 int main()
15 {
16     IO;int T,n;
17     cin>>T;
18     while(T--)
19     {
20         int x1,y1,x2,y2;
21         cin>>n;
22         for(int i=0;i<n;i++)
23             cin>>p[i].x>>p[i].y;
24         sort(p,p+n,cmp);
25         if(p[n/2].x!=p[n/2-1].x)
26             x1=p[n/2-1].x,y1=m,x2=p[n/2].x,y2=-m;
27         else
28             x1=p[n/2].x-1,y1=p[n/2].y+m,x2=p[n/2].x+1,y2=p[n/2-1].y-m;
29         cout<<x1<<' '<<y1<<' '<<x2<<' '<<y2<<endl;
30     }
31     return 0;
32 }