poj 1654 Area （多边形求面积）

 1 #include <stdio.h>
 2 #include <string.h>
 3 #include <stdlib.h>
 4 #include <iostream>
 5 #include <algorithm>
 6 #include <math.h>
 7 
 8 #define MAXX 1000002
 9 #define eps 1e-6
10 typedef struct
11 {
12     double x;
13     double y;
14 } point;
15 
16 double crossProduct(point a,point b,point c)
17 {
18     return (c.x-a.x)*(b.y-a.y)-(c.y-a.y)*(b.x-a.x);
19 }
20 
21 bool dy(double x,double y)
22 {
23     return x>y+eps;
24 }
25 bool xy(double x,double y)
26 {
27     return x<y-eps;
28 }
29 bool dd(double x,double y)
30 {
31     return fabs(x-y)<eps;
32 }
33 
34 int main()
35 {
36     int n,m,i,j,x,y;
37     scanf("%d",&n);
38     char str[MAXX];
39     int move[10][2]= {{0,0},{-1,-1},{0,-1},{1,-1},{-1,0},{0,0},{1,0},{-1,1},{0,1},{1,1}};
40     for(i=0; i<n; i++)
41     {
42         scanf("%s",str);
43         int len=strlen(str);
44         int x1=0,y1=0,x2,y2;
45         long long ans=0;
46         for(j=0; j<len-1; j++)
47         {
48             x2=x1+move[str[j]-‘0‘][0];
49             y2=y1+move[str[j]-‘0‘][1];
50             ans+=((x1*y2)-(x2*y1));
51             x1=x2;
52             y1=y2;
53         }
54         ans = ans > 0 ? ans : (-1)*ans;
55         if(ans == 0)
56             printf("0\n");
57             else if(ans % 2 == 0)
58             printf("%lld\n",ans/2);
59             else if(ans % 2 != 0)
60             printf("%lld.5\n",ans/2);
61     }
62 return 0;
63 }