ural 1207 Median on the Plane

极角排序

 1 #include <cstdio>

 2 #include <cstring>

 3 #include <algorithm>

 4 #include <cmath>

 5 #define maxn 30000

 6 using namespace std;

 7 

 8 struct point

 9 {

10     double x,y;

11     int num;

12 }p[maxn];

13 point pp;

14 double cross(const point &a,const point &b,const point &c)

15 {

16     return (b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x);

17 }

18 bool cmp(const point &a,const point &b)

19 {

20     if(cross(p[0],a,b)>0) return 0;

21     else return 1;

22 }

23 int main()

24 {

25     int n;

26     int k=0;

27     scanf("%d",&n);

28     for(int i=0; i<n; i++)

29     {

30         scanf("%lf%lf",&p[i].x,&p[i].y);

31         p[i].num=i+1;

32         if(p[i].y<p[k].y||(p[k].y==p[i].y&&p[i].x<p[k].x)) k=i;

33     }

34     swap(p[0],p[k]);

35     sort(p+1,p+n,cmp);

36     printf("%d %d\n",p[0].num,p[n/2].num);

37     return 0;

38 }

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