給一個凸包,要求逆時針排序,剛開始一直因為極角排序就是逆時針的,是以一直wa,後來發現極角排序距離相同是,排的是随機的,是以要對末尾角度相同的點重新排一次
#include<map>
#include<set>
#include<cmath>
#include<queue>
#include<stack>
#include<vector>
#include<cstdio>
#include<cassert>
#include<iomanip>
#include<cstdlib>
#include<cstring>
#include<iostream>
#include<algorithm>
#define pi acos(-1.0)
#define ll long long
#define mod 1000000007
#define ls l,m,rt<<1
#define rs m+1,r,rt<<1|1
#pragma comment(linker, "/STACK:1024000000,1024000000")
using namespace std;
const double g=10.0,eps=1e-12;
const int N=100000+10,maxn=500+100,inf=0x3f3f3f;
struct point{
double x,y;
};
point p[N],s[N];
int n;
inline bool zero(double x)
{
return fabs(x)<eps;
}
double dir(point p1,point p2,point p3)
{
return (p3.x-p1.x)*(p2.y-p1.y)-(p3.y-p1.y)*(p2.x-p1.x);
}
double dis(point p1,point p2)
{
return sqrt((p2.x-p1.x)*(p2.x-p1.x)+(p2.y-p1.y)*(p2.y-p1.y));
}
bool comp(point p1,point p2)
{
double te=dir(p[0],p1,p2);
if(te<0)return 1;
if(zero(te)&&dis(p[0],p1)<dis(p[0],p2))return 1;
return 0;
}
bool comp1(point p1,point p2)
{
return dis(p[0],p1)>dis(p[0],p2);
}
void Graham()
{
int pos;
double minx=inf,miny=inf;
for(int i=0;i<n;i++)
{
if(p[i].x<minx||(p[i].x<minx&&p[i].y<miny))
{
minx=p[i].x;
miny=p[i].y;
pos=i;
}
}
swap(p[0],p[pos]);
sort(p+1,p+n,comp);
int k=n-1;
while(1){
if(k>=1&&zero(dir(p[0],p[k-1],p[k])))k--;
else break;
}
sort(p+k,p+n,comp1);
cout<<n<<endl;
for(int i=0;i<n;i++)
cout<<p[i].x<<" "<<p[i].y<<endl;
}
int main()
{
ios::sync_with_stdio(false);
cin.tie(0);
cout<<setiosflags(ios::fixed)<<setprecision(0);
int t;
cin>>t;
while(t--){
cin>>n;
string c;
for(int i=0;i<n;)
{
cin>>p[i].x>>p[i].y>>c;
if(c[0]=='Y')i++;
else n--;
}
Graham();
}
return 0;
}
/*********************
1
5
1 1 Y
1 -1 Y
0 0 N
-1 -1 Y
-1 1 Y
3
12
0 0 Y
2 0 Y
1 0 Y
3 0 Y
3 3 Y
1 3 Y
2 3 Y
3 1 Y
3 2 Y
0 1 Y
0 2 Y
0 3 Y
3
0 0 Y
1000000000 1000000000 Y
1000000000 0 Y
8
0 -2 Y
1 -1 Y
2 0 Y
1 1 Y
0 2 Y
-1 1 Y
-2 0 Y
-1 -1 Y
*********************/
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