zoj1032 Area 2

1. //zoj1032 Area 2
2. //Accepted 1032 C++ 00:00.00 392K 
3. #include <stdio.h>
4. #define MAXN 100
5.  
6. struct point{ double x,y;};
7.  
8. double xmult(double x1,double y1,double x2,double y2){ return (x1*y2-y1*x2);}
9. int gcd(int a,int b) { return b?gcd(b,a%b):a;}
10. int abs(int x) { return x>0?x:(0-x);}
11.  
12. double area_polygon(int n, point *p)
13. {
14.        int i;
15.        double ret=0;
16.        for (i=0; i<n; ++i)
17.               ret += xmult(p[i].x,p[i].y,p[i+1].x,p[i+1].y);
18.        ret += xmult(p[n-1].x,p[n-1].y,p[0].x,p[0].y);
19.        return ret/2;
20. }
21.  
22. void solve()
23. {
24.        int i,n;
25.        point p[MAXN+1];
26.        int c,e;
27.        double a;
28.        int dx,dy;
29.        scanf ("%d",&n);
30.        p[0].x = p[0].y = 0;
31.        e = 0;
32.        for (i=0; i<n; ++i){
33.               scanf ("%d %d",&dx,&dy);
34.               e += gcd(abs(dx),abs(dy));
35.               p[i+1].x = p[i].x+dx;
36.               p[i+1].y = p[i].y+dy;
37.        }
38.        a = area_polygon(n+1,p);
39.        c = (int)(a+1-0.5*(double)e);
40.        printf ("%d %d %.1lf/n/n",c,e,a);
41. }
42.  
43. int main()
44. {
45. #ifdef ONLINE_JUDGE
46. #else
47.        freopen("1032.txt","r",stdin);
48. #endif
49.        int i,t;
50.        while (scanf ("%d",&t) != EOF)
51.               for (i=1; i<=t; ++i){
52.                      printf ("Scenario #%d:/n",i);
53.                      solve();
54.               }
55. #ifdef ONLINE_JUDGE
56. #else
57.        fclose(stdin);
58. #endif
59.        return 0;
60. }