Poj Solution 1265

http://poj.org/problem?id=1265

//* @author: ccQ.SuperSupper
import java.io.*;
import java.util.*;
class Point{
    int x,y;
}
public class Main {
    
    static final int N = 100+10;
    static int n;
    static Point Area[] = new Point[N];
    static void start(){
        for(int i=0;i< N;++i)
            Area[i] = new Point();
    }
public static void main(String []args) throws Exception{
        
    int t,cs=1,i,x,y;
    
    StreamTokenizer cin = new StreamTokenizer(new BufferedReader(new InputStreamReader(System.in)));
    start();
    t = Get_Num(cin);
    while(t--!=0){
        n = Get_Num(cin);
        Area[0].x = Area[0].y = 0;
        for(i=1;i<=n;++i){
            Area[i].x = Get_Num(cin)+Area[i-1].x;
            Area[i].y = Get_Num(cin)+Area[i-1].y;
        }
        solve(cs++);
    }
}
    static int Get_Num(StreamTokenizer cin) throws Exception{
        cin.nextToken();
        return (int) cin.nval;
    }
    static int GCD(int a,int b){
        if(b==0) return a;
        return GCD(b,a%b);
    }
    static int node_in_line(Point a,Point b){
        int x,y;
        x = abs(a.x-b.x);
        y = abs(a.y-b.y);
        return GCD(x,y);
    }
    static int abs(int a){
        if(a>=0) return a;
        return -a;
    }
    static int get_area(Point a,Point b,Point c){
        return (c.x-a.x)*(b.y-a.y) - (b.x-a.x)*(c.y-a.y);
    }
    static void solve(int cs){
        int I,E=0,area=0,i;
        for(i=0;i< n;++i){
            E+=node_in_line(Area[i],Area[(i+1)%n]);
        }
        for(i=2;i< n;++i){
            area += get_area(Area[0],Area[i-1],Area[i]);
        }
        area = abs(area);
        I = (area-E+2)/2;
        
        System.out.print("Scenario #"+cs+":n"+I+" "+E+" ");
        if(area%2==0) System.out.println(area/2+".0n");
        else System.out.println(area/2+".5n");
    }
}