多边形求面积的题目。。
code：
1 /* 2 Time:2013-04-06 15:02:38 3 State:Accepted 4 */ 5 #include<iostream> 6 #include<fstream> 7 #include<cstring> 8 #include<cstdlib> 9 #include<cstdio> 10 #include<string> 11 #include<cmath> 12 #include<algorithm> 13 using namespace std; 14 typedef __int64 LL; 15 struct oo{ LL x , y; }; 16 int T; 17 oo a, b, c; 18 LL ans; 19 20 LL work_x(const oo a,const oo b){ 21 return b.x*a.y - a.x * b.y; 22 } 23 24 void solve(){ 25 char c; 26 a.x = a.y = 0; 27 b.x = b.y = 0; 28 ans = 0; 29 scanf("%c", &c); 30 while (scanf("%c", &c) != EOF && c != '5'){ 31 if (c == '8'){ a.x = b.x; a.y = b.y + 1;} 32 if (c == '2'){ a.x = b.x; a.y = b.y - 1;} 33 if (c == '6'){ a.x = b.x + 1; a.y = b.y;} 34 if (c == '4'){ a.x = b.x - 1; a.y = b.y;} 35 if (c == '9'){ a.x = b.x + 1; a.y = b.y + 1;} 36 if (c == '7'){ a.x = b.x - 1; a.y = b.y + 1;} 37 if (c == '3'){ a.x = b.x + 1; a.y = b.y - 1;} 38 if (c == '1'){ a.x = b.x - 1; a.y = b.y - 1;} 39 ans += work_x(a , b); 40 b = a; 41 } 42 if (ans < 0) ans *= -1; 43 if (ans & 1) printf("%I64d.5\n",ans / 2); 44 else printf("%I64d\n", ans / 2); 45 } 46 47 int main(){ 48 freopen("poj1654.in","r",stdin); 49 freopen("poj1654.out","w",stdout); 50 scanf("%d",&T); 51 for (int i = 1; i <= T; ++i){ 52 solve(); 53 } 54 fclose(stdin); fclose(stdout); 55 }