Go: package main

import (
        "fmt"
)

func main() {
        var x1, y1, x2, y2, x3, y3, px, py float64
        var oax, oay, obx, oby, opx, opy float64
        var det float64
        var s, t float64

        for {
                _, err := fmt.Scanf("%f %f %f %f %f %f %f %f", &x1, &y1, &x2, &y2, &x3, &y3, &px, &py)
                if err != nil {
                        break
                }
                oax = x2 - x1
                oay = y2 - y1
                obx = x3 - x1
                oby = y3 - y1
                opx = px - x1
                opy = py - y1
                det = oax*oby - obx*oay

                if det == 0 {
                        fmt.Printf("NO\n")
                } else {
                        s = (oby*opx - obx*opy) / det
                        t = (oax*opy - oay*opx) / det

                        if (s+t < 1 && s > 0 && t > 0) {
                                fmt.Printf("YES\n")
                        } else {
                                fmt.Printf("NO\n")
                        }
                }
        }
}

C++: #include <cstdio>
#include <vector>
#include <algorithm>
#include <complex>

using namespace std;

static const double EPS=1e-12;
static const double INF=1e24;

using Point=complex<double>;
using Plane=vector<Point>;

namespace std {
    bool operator<(const Point &a, const Point &b) {
        return real(a)!=real(b)? real(a)<real(b) : imag(a)<imag(b);
    }
}

double cross_prod(const Point &a, const Point &b) {
    return imag(conj(a)*b);
}

double dot_prod(const Point &a, const Point &b) {
    return real(conj(a)*b);
}

struct Line: public pair<Point, Point> {
    Line() {}
    Line(const Point &a, const Point &b) {
        first = a;
        second = b;
    }
};

struct LineSeg: public pair<Point, Point> {
    LineSeg() {}
    LineSeg(const Point &a, const Point &b) {
        first = a;
        second = b;
    }
};

struct Circle {
    Point p;
    double r;
    Circle() {}
    Circle(const Point &p, const double r): p(p), r(r) {}
};

enum CCWiseState {
    ONLINE_FRONT=-2,
    CLOCKWISE,
    ON_SEGMENT,
    COUNTER_CLOCKWISE,
    ONLINE_BACK,
};

CCWiseState ccwise(Point a, Point b, Point c) {
    b -= a; c -= a;

    if (cross_prod(b, c) > 0) {
        return COUNTER_CLOCKWISE;
    } else if (cross_prod(b, c) < 0) {
        return CLOCKWISE;
    } else if (dot_prod(b, c) < 0) {
        return ONLINE_BACK;
    } else if (norm(b) < norm(c)) {
        return ONLINE_FRONT;
    } else {
        return ON_SEGMENT;
    }
}

bool includes(const Point &A, const Point &B, const Point &C, const Point &P) {
    // returns whether triangle ABC includes point P
    CCWiseState tmp=ccwise(A, P, B);
    if (tmp != ccwise(B, P, C)) return false;
    if (tmp != ccwise(C, P, A)) return false;

    return true;
}

bool testcase_ends() {
    double x, y;
    if (scanf("%lf %lf", &x, &y) == EOF)
        return 1;

    Point A(x, y);
    scanf("%lf %lf", &x, &y);
    Point B(x, y);
    scanf("%lf %lf", &x, &y);
    Point C(x, y);

    scanf("%lf %lf", &x, &y);
    Point P(x, y);

    printf("%s\n", includes(A, B, C, P)? "YES":"NO");
    return 0;
}

int main() {
    int solved=0;
    while (!testcase_ends())
        ++solved;

    return !solved;
}

C++: #include <iostream>
#include <iomanip>
#include <vector>
#include <string>
#include <stack>
#include <queue>
#include <deque>
#include <set>
#include <map>
#include <algorithm>
#include <sstream>
#include <cstdlib>
#include <cstring>
#include <functional>
#include <numeric>
#include <cmath>
#include <climits>
#include <limits>
#include <cfloat>
#include <fstream>
#include <complex>

using namespace std;

typedef complex<double> P;

#define EPS (1e-10)
#define EQ(a,b) (abs((a)-(b)) < EPS)

// OÏ (cross product) : a~b = |a||b|sinÆ
double cross(P a, P b) {
  return (a.real() * b.imag() - a.imag() * b.real());
}

int main()
{
//	cut here before submit 
//	freopen("testcase.pt", "r", stdin);
	string str = "";

	while (getline (cin, str )){
		if (str.empty() ){
			break;
		} // end if
		double x1, y1, x2, y2, x3, y3, xp, yp;
		stringstream ss (str );
		ss >> x1 >> y1 >> x2 >> y2 >> x3 >> y3 >> xp >> yp;
		P a(x1, y1), b(x2, y2), c(x3, y3 ), p(xp, yp);
		P Vab = b - a, Vbc = c - b, Vca = a - c;
		P Vap = p - a, Vbp = p - b, Vcp = p - c;
		
		if (cross (Vab, Vap ) > 0. && cross (Vbc, Vbp ) > 0. && cross (Vca, Vcp ) > 0.){
			cout << "YES" << endl;
		}else{
			cout << "NO" << endl;
		} // end if
	} // end loop

	return 0;
}

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

int judge(pair<double, double> p1, pair<double, double> p2){
	int S = p1.first*p2.second - p2.first*p1.second;
	if (0 < S) return 1;
	if (0 > S) return -1;
	if (0 == S) return 0;
}

int main(){
	pair<double, double> A, B, C, P;

	while (cin >> A.first >> A.second >> B.first >> B.second >> C.first >> C.second >> P.first >> P.second){
		pair<double, double> AB, BC, CA, AP, BP, CP;
		AB = { B.first - A.first, B.second - A.second };
		BC = { C.first - B.first, C.second - B.second };
		CA = { A.first - C.first, A.second - C.second };
		AP = { P.first - A.first, P.second - A.second };
		BP = { P.first - B.first, P.second - B.second };
		CP = { P.first - C.first, P.second - C.second };
		
		if (judge(AP, AB) == judge(BP, BC) && judge(BP, BC) == judge(CP, CA) && judge(CP, CA) == judge(AP, AB)){
			cout << "YES" << endl;
		}
		else{
			cout << "NO" << endl;
		}
	}

	return 0;
}

C++: #include <iostream>

using namespace std;

typedef struct _Point {
	double x;
	double y;
} Point;

typedef struct _Line {
	Point a;
	Point b;
} Line;

typedef struct _Triangle {
	Point a;
	Point b;
	Point c;
} Triangle;

int side(Point p, Line l) {
	int n = p.x * (l.a.y - l.b.y) + l.a.x * (l.b.y - p.y) + l.b.x * (p.y - l.a.y);
	if (n > 0) return 1;
	else if (n < 0) return -1;
	else return 0;
}

bool pointInaTriangle(Point p, Triangle t) {
	Line ab, bc, ca;
	ab.a = t.a; ab.b = t.b;
	bc.a = t.b; bc.b = t.c;
	ca.a = t.c; ca.b = t.a;
	int pab = side(p, ab);
	int pbc = side(p, bc);
	int pca = side(p, ca);
	if (0 < pab && 0 < pbc && 0 < pca)
		return true;
	if (0 > pab && 0 > pbc && 0 > pca)
		return true;
	if (0 <= pab && 0 <= pbc && 0 <= pca)
		return true;
	if (0 >= pab && 0 >= pbc && 0 >= pca)
		return true;
	return false;
}

int main() {
	Triangle t;
	Point p;
	while (cin >> t.a.x >> t.a.y >> t.b.x >> t.b.y >> t.c.x >> t.c.y >> p.x >> p.y) {
		if (pointInaTriangle(p, t) == true)
			cout << "YES" << endl;
		else
			cout << "NO" << endl;
	}
	return 0;
}

C++: #include <iostream>
#include <sstream>
#include <string>
#include <vector>
#include <deque>
#include <stack>
#include <queue>
#include <set>
#include <map>
#include <bitset>
#include <algorithm>
#include <numeric>
#include <complex>
#include <functional>
#include <utility>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>

using namespace std;

#define dump(n) cout<<"# "<<#n<<"="<<(n)<<endl
#define debug(n) cout<<__FILE__<<","<<__LINE__<<": #"<<#n<<"="<<(n)<<endl
#define repi(i,a,b) for(int i=int(a);i<int(b);i++)
#define rep(i,n) repi(i,0,n)
#define iter(c) __typeof((c).begin())
#define tr(c,i) for(iter(c) i=(c).begin();i!=(c).end();i++)
#define allof(c) (c).begin(),(c).end()
#define mp make_pair

typedef long long ll;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<string> vs;
typedef pair<int,int> pii;

double cross(double x1,double y1,double x2,double y2)
{
	return x1*y2-x2*y1;
}

int ccw(double x1,double y1,double x2,double y2,double x3,double y3)
{
	return cross(x2-x1,y2-y1,x3-x1,y3-y1)>=0;
}

int main()
{
	for(double x[4],y[4];scanf("%lf%lf%lf%lf%lf%lf%lf%lf",x,y,x+1,y+1,x+2,y+2,x+3,y+3)==8;){
		int counter=0;
		rep(i,3)
			counter+=ccw(x[i],y[i],x[(i+1)%3],y[(i+1)%3],x[3],y[3]);
		
		cout<<(counter%3==0?"YES":"NO")<<endl;
	}
	
	return 0;
}