poj2954
题目大意：给定三角形的三个顶点，求内部点有多少。。
思路：先叉积求面积，然后用 S=a + b/2 - 1（皮克公式），a为内部点，b为边上点，求出a。。
code：
1 /* 2 State:Accepted 3 Time:2013-04-06 16:40:55 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 struct oo{ int x , y; }; 15 oo a, b, c; 16 17 int work_x(int x2, int y2, int x1, int y1){ 18 return x1*y2 - x2*y1; 19 } 20 21 int gcd(int a, int b){ 22 if (a % b == 0) return b; 23 else return gcd(b , a % b); 24 } 25 26 int work_p(const oo a, const oo b){ 27 int dx = a.x - b.x; 28 int dy = a.y - b.y; 29 int d; 30 if (dx == 0) d = abs(dy); 31 else if (dy == 0) d = abs(dx); 32 else d = gcd(abs(dx), abs(dy)); 33 return d; 34 } 35 void solve(){ 36 int squre = abs(work_x(b.x - a.x, b.y - a.y, c.x - a.x, c.y - a.y)); 37 int tm = work_p(a, b) + work_p(b,c) + work_p(a,c); 38 int ans = (squre + 2 - tm) / 2; 39 printf("%d\n",ans); 40 } 41 42 int main(){ 43 freopen("poj2954.in","r",stdin); 44 freopen("poj2954.out","w",stdout); 45 while (scanf("%d%d%d%d%d%d",&a.x, &a.y, &b.x, &b.y, &c.x, &c.y) != EOF){ 46 if (!a.x && !a.y && !b.x && !b.y && !c.x && !c.y) break; 47 solve(); 48 } 49 fclose(stdin); fclose(stdout); 50 }
