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 <iostream>
#include <stdio.h>
#include <utility>
using namespace std;
int main(){
    double px,py;
    double tx[3],ty[3];
    bool flag;
    bool v[3];
    while(scanf("%lf %lf %lf %lf %lf %lf %lf %lf",&tx[0],&ty[0],&tx[1],&ty[1],&tx[2],&ty[2],&px,&py) == 8){
        for(int i=0;i<3;i++){
            tx[i]=tx[i]-px;
            ty[i]=ty[i]-py;
        }
        for(int i=0;i<3;i++){
            if((tx[i%3]*ty[(i+1)%3])-(ty[i%3]*tx[(i+1)%3])<0){
                v[i]=true;
            }else{
                v[i]=false;
            }
        }
         
        if(v[0]!=v[1]){
            cout<<"NO"<<endl;
        }else if(v[1]!=v[2]){
            cout<<"NO"<<endl;
        }else {
            cout<<"YES"<<endl;
        }
    }
    return 0;
}

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

using namespace std;

float hang(float a,float b,float c,float d,float e,float f){
    float A;
    A=(a*d + b*e + c*f - e*d - b*c - a*f)/2;
    return A;      
}

int main()
{
    float x1,y1,x2,y2,x3,y3,xp,yp,s1,s2,s3,s;
    while(cin>>x1>>y1>>x2>>y2>>x3>>y3>>xp>>yp){
       s1=hang(xp,yp,x2,y2,x3,y3);
       s2=hang(x1,y1,xp,yp,x3,y3);
       s3=hang(x1,y1,x2,y2,xp,yp);
       s=hang(x1,y1,x2,y2,x3,y3);
       if(s==(s1+s2+s3))cout<<"YES"<<endl;
       else cout<<"NO"<<endl;                                                   
    }
    return 0;
}

C++: #include<iostream>
#include<cmath>
#include<algorithm>
#include<utility>
using namespace std;
double x,y;
bool C(double a,double b,double c,double d,double e,double f)
{
	pair<double,int>p[3];
	p[0]=make_pair(atan2(d-b,c-a),0);
	p[1]=make_pair(atan2(f-b,e-a),1);
	p[2]=make_pair(atan2(y-b,x-a),2);
	sort(p,p+3);
	return p[1].second==2;
}
int main()
{
	double a,b,c,d,e,f;
	for(;cin>>a>>b>>c>>d>>e>>f>>x>>y;)
	{
		cout<<(C(a,b,c,d,e,f)&&C(c,d,e,f,a,b)&&C(e,f,a,b,c,d)?"YES":"NO")<<endl;
	}
}

C++: #include <iostream>
#include <math.h>
#include <algorithm>
#include <string>
#include <stack>
#include <queue>
#include <set>
#include <cstdio>
#include <string.h>
using namespace std;

#define FOR(i, n) for(int i = 0; i < n; i++)
#define bit(i) static_cast<bitset<8> >(i)

typedef long long ll;
typedef unsigned long long ull;
typedef vector<int> VI;
typedef vector<string> VS;
typedef pair<int, int> PII;
typedef pair<long long, long long>PLL;
typedef queue<int> QI;
typedef priority_queue<int> maxpq;
typedef priority_queue<int, vector<int>, greater<int> > minpq;

struct edge{int to, cost;};

void begin(){cin.tie(0); ios::sync_with_stdio(false);};
int gcd(int a, int b){if(a%b==0){return(b);}else{return(gcd(b,a%b));}};
int lcm(int m, int n){if((0 == m)||(0 == n)){return 0;} return ((m / gcd(m, n)) * n);};
unsigned long long comb(long n, long m){unsigned long long c = 1; m = (n - m < m ? n - m : m);
    for(long ns = n - m + 1, ms = 1; ms <= m; ns ++, ms ++){c *= ns; c /= ms;} return c;};

// ワーシャルフロイド法
void warshallFloyd(int d[100][100], int n){
    for(int k = 0; k < n; ++k)
        for(int i = 0; i < n; ++i)
            for(int j = 0; j < n; ++j)
                if(d[i][k] != -1 && d[k][j] != -1){
                    if(d[i][j] == -1){
                        d[i][j] = d[i][k] + d[k][j];
                    }else{
                        d[i][j] = min(d[i][j], d[i][k] + d[k][j]);
                    }
                }
};


// d:隣接行列  n:グラフのサイズ  s:始点  dist:始点からの距離が入る配列
void dijkstra(int d[1000][1000], int n, int s, int dist[1000]){
    FOR(i, n) dist[i] = -1;
    dist[s] = 0;
    priority_queue<PII, vector<PII>, greater<PII> > q;
    q.push(PII(0, s));
    while (!q.empty()) {
        PII p = q.top(); q.pop();
        int i = p.second;
        if(dist[i] < p.first) continue;
        for(int j = 0; j < n; j++){
            if(d[i][j] == -1) continue;
            if(dist[j] == -1){
                dist[j] = dist[i] + d[i][j];
                q.push(PII(dist[j], j));
            }else if(dist[j] > dist[i] + d[i][j]){
                dist[j] = dist[i] + d[i][j];
                q.push(PII(dist[j], j));
            }
        }
    }
};

// 線分の交差判定
bool isCross(int x1, int y1, int x2, int y2, int x3, int y3, int x4, int y4){
    // 並行な場合
    int m = (x2-x1)*(y4-y3)-(y2-y1)*(x4-x3);
    if(m == 0) return false;
    // 媒介変数の値が0より大きく1以下なら交差する、これは問題の状況によって変わるかも。
    double r =(double)((y4-y3)*(x3-x1)-(x4-x3)*(y3-y1))/m;
    double s =(double)((y2-y1)*(x3-x1)-(x2-x1)*(y3-y1))/m;
    return (0 < r && r <= 1 && 0 < s && s <= 1);
};

// 外積の計算 AB CD
int crossProdct(int ax, int ay, int bx, int by, int cx, int cy, int dx, int dy){
    int abx = bx - ax;
    int aby = by - ay;
    int cdx = cx - dx;
    int cdy = cy - dy;
    return abx * cdy - cdx - aby;
};

double crossProdct(double ax, double ay, double bx, double by, double cx, double cy, double dx, double dy){
    double abx = bx - ax;
    double aby = by - ay;
    double cdx = dx - cx;
    double cdy = dy - cy;
    return abx * cdy - cdx - aby;
};

// 三角形の内部判定
bool inTriangle(int ax, int ay, int bx, int by, int cx, int cy, int px, int py){
    int abx = bx - ax;
    int aby = by - ay;
    int bcx = cx - bx;
    int bcy = cy - by;
    int cax = ax - cx;
    int cay = ay - cy;
    
    int apx = px - ax;
    int apy = py - ay;
    int bpx = px - bx;
    int bpy = py - by;
    int cpx = px - cx;
    int cpy = py - cy;
    
    int c1 = abx * bpy - aby * bpx;
    int c2 = bcx * cpy - bcy * cpx;
    int c3 = cax * apy - cay * apx;
    return (c1 > 0 && c2 > 0 && c3 > 0) || (c1 < 0 && c2 < 0 && c3 < 0);
};

bool inTriangle(double ax, double ay, double bx, double by, double cx, double cy, double px, double py){
    double c1 = crossProdct(ax, ay, bx, by, bx, by, px, py);
    double c2 = crossProdct(bx, by, cx, cy, cx, cy, px, py);
    double c3 = crossProdct(cx, cy, ax, ay, ax, ay, px, py);
    return (c1 > 0 && c2 > 0 && c3 > 0) || (c1 < 0 && c2 < 0 && c3 < 0);
};

void cp(int a1[], int a2[], int l){FOR(i, l) a2[i] = a1[i];};



/**
 * start
 * @author yoshikyoto
 */
int main(int argc, const char * argv[]){
    begin();
    double ax, ay, bx, by, cx, cy, px, py;
    while(cin >> ax >> ay >> bx >> by >> cx >> cy >> px >> py){
        if(inTriangle(ax, ay, bx, by, cx, cy, px, py)){
            cout << "YES" << endl;
        }else{
            cout << "NO" << endl;
        }
    }
}