Go: package main

import "fmt"

func main() {
	var x1, x2, x3, y1, y2, y3, xp, yp float64
	for {
		v, _ := fmt.Scanf("%f %f %f %f %f %f %f %f", &x1, &y1, &x2, &y2, &x3, &y3, &xp, &yp)
		// println(x1, x2, x3, y1, y2, y3, xp, yp)
		if v != 8 {
			break
		}
		ok1 := true
		ok2 := true
		if (x2-x1)*(yp-y1)-(xp-x1)*(y2-y1)<0 {
			ok1 = false
		} else {
			ok2 = false
		}
		if (x3-x2)*(yp-y2)-(xp-x2)*(y3-y2)<0 {
			ok1 = false
		} else {
			ok2 = false
		}
		if (x1-x3)*(yp-y3)-(xp-x3)*(y1-y3)<0 {
			ok1 = false
		} else {
			ok2 = false
		}
		if ok1 || ok2 {
			fmt.Println("YES")
		} else {
			fmt.Println("NO")
		}
	}
}

C++: #include <bits/stdc++.h>
using namespace std ;

#define pb(n) push_back(n)
#define fi first
#define se second
#define X real()
#define Y imag()
#define all(r) (r).begin(),(r).end()
#define gsort(st,en) sort((st),(en),greater<int>())
#define vmax(ary) *max_element(all(ary))
#define vmin(ary) *min_element(all(ary))
#define debug(x) cout<<#x<<": "<<x<<endl
#define fcout(n) cout<<fixed<<setprecision((n))
#define scout(n) cout<<setw(n)
#define vary(type,name,size,init) vector< type> name(size,init)

#define rep(i,n) for(int i = 0; i < (int)(n);++i)
#define REP(i,a,b) for(int i = (a);i < (int)(b);++i)
#define repi(it,array) for(auto it = array.begin(),end = array.end(); it != end;++it)
#define repa(n,array) for(auto &n :(array))

using ll = long long;
using vi = vector<int>;
using vl = vector<ll>;
using dict = map<string,int>;
using comd = complex<double>;
using pii = pair<int,int> ;

constexpr int imax = ((1<<30)-1)*2+1 ;
constexpr int inf = 100000000;
constexpr double PI = acos(-1.0) ;
double eps = 1e-10 ;
const int dy[] = {-1,0,1,0};
const int dx[] = {0,-1,0,1};

inline bool value(int x,int y,int w,int h){
  return (x >= 0 && x < w && y >= 0 && y < h);
}

double CalcDist(comd p1, comd p2){
  return sqrt(pow(p1.X - p2.X,2.0) + pow(p1.Y -p2.Y,2.0));
}

template<typename T>
void Unique(vector<T> &v){
  sort(all(v));
  v.erase(all(v),v.end());
}

template<typename T>
T ston(string& str, T n){
  istringstream sin(str) ;
  T num ;
  sin >> num ;
  return num ;
}

void Ans(bool f){
  if(f) cout << "YES"<<endl;
  else cout << "NO"<<endl;
}

double EPS = 1e-10;
double add(double a, double b){
  if(abs(a+b) < EPS* (abs(a) + abs(b))) return 0;
  return a+b;
}
struct P{
  double x,y;
  P(){}
  P(double _x,double _y):x(_x),y(_y){}
  P operator + (P p){
    return P(add(x,p.x) ,add(y,p.y));
  }
  P operator - (P p){
    return P(add(x,-p.x) ,add(y,-p.y));
  }
  P operator * (double d){
    return P(x * d,y * d);
  }
  double norm(){
    return x*x + y*y;
  }
  double dot(P p){
    return add(x * p.x,y*p.y);
  }
  double det(P p){
    return add(x*p.y,-y*p.x);
  }
  double dist2(P p){
    return ((*this-p).x * (*this-p).x) + ((*this-p).y * (*this-p).y);
  }
  double GetSlope(P &p){
    P tmp = *this - p;
    return tmp.y/tmp.x;
  }
};
//???????????????????????¨?????????
bool on_seg(P p1,P p2,P q){
  return (p1-q).det(p2-q) == 0 && (p1-q).dot(p2-q) <= 0;
}

bool check(P p1,P p2,P p3, P p4){
  P a = p1 - p2,b = p3 - p2, p = p4 - p2;
  double theta1 = acos(a.dot(b)/(a.norm() * b.norm()));
  double theta2 = acos(b.dot(a)/(a.norm() * b.norm()));
  double thetap = acos(a.dot(p)/(a.norm() * p.norm()));
  double thetaq = acos(b.dot(p)/(a.norm() * p.norm()));
//   debug(theta1);
//   debug(theta2);
//   debug(thetap);
//   debug(thetaq);
  return thetap <= theta1 && thetaq <= theta1;
}

int main(){
  cin.tie(0);
  ios::sync_with_stdio(false);
  double a,b,c,d,e,f,xp,yp;
  while(cin >> a >> b >> c >> d >> e >> f >> xp >> yp){
    bool flag = true;
//     double acx = c-a,abx = e-a,acy = d-b,aby = f-b,apx = xp-a,apy = yp - b;
    P p1 = P(a,b),p2 = P(c,d),p3 = P(e,f),p4 = P(xp,yp);
    Ans(check(p1,p2,p3,p4) && check(p1,p3,p2,p4) && check(p3,p1,p2,p4));
  }
  return 0;
}

C++: #include <iostream>
#include <cmath>
using namespace std;

double cross_prod(double x0, double y0, double x1, double y1) {
	return x0 * y1 - x1 * y0;
}

int main() {
	double x[4], y[4];
	while(cin >> x[0] >> y[0]) {
		for(int i = 1; i < 4; i++)
			cin >> x[i] >> y[i];
		double a, b;
		a = b = 0;
		for(int i = 0; i < 3; i++) {
			double tmp;
			tmp = cross_prod(x[i]-x[4], y[i]-y[4], x[(i+1)%3]-x[4], y[(i+1)%3]-y[4]);
			a += tmp;
			b += abs(tmp);
		}
		if(abs(a-b) < 1e-7)
			cout << "YES" << endl;
		else
			cout << "NO" << endl;
	}
}

C++: #include <iostream>
using namespace std;

class Vector2{
public:
	Vector2(){}
	Vector2( double aX, double aY ) : x( aX ), y( aY ){}

	double cross( Vector2& a ){
		return ( x * a.y ) - ( y * a.x );
	}

	double x;
	double y;
};

int main(){
	Vector2 p0, p1, p2, q;

	while ( cin >> p0.x >> p0.y >> p1.x >> p1.y >> p2.x >> p2.y >> q.x >> q.y ){
		bool isInner = false;
		Vector2 ab( p1.x - p0.x, p1.y - p0.y );
		Vector2 bc( p2.x - p1.x, p2.y - p1.y );
		Vector2 ca( p0.x - p2.x, p0.y - p2.y );
		Vector2 ap( q.x - p0.x, q.y - p0.y );
		Vector2 bp( q.x - p1.x, q.y - p1.y );
		Vector2 cp( q.x - p2.x, q.y - p2.y );

		if( ( (ab.cross( ap ) > 0 ) && (bc.cross( bp ) > 0 ) && (ca.cross( cp ) > 0 ) ) ||
			( (ab.cross( ap ) < 0 ) && (bc.cross( bp ) < 0 ) && (ca.cross( cp ) < 0 ) ) ){
			isInner = true;
		}

		cout << ( isInner ? "YES" : "NO" ) << endl;
	}

	return 0;
}

C++: #include <iostream>
#include <algorithm>
#include <deque>

using namespace std;

int main()
{
	double x[3],y[3],xp,yp;
	
	while(cin>>x[0]>>y[0]>>x[1]>>y[1]>>x[2]>>y[2]>>xp>>yp)
	{
		double a,b,c,d;
		sort(x,x+3);
		sort(y,y+3);
		a=x[0],b=x[2],c=y[0],d=y[2];

		int ture=0;
		if(a<xp && xp<b) ture++;
		if(c<yp && yp<d)ture++;

		if(ture==2)cout<<"YES"<<endl;
		else cout<<"NO"<<endl;

	}

	return 0;
}