poj 2954 Triangle

 1 #include<iostream>
 2 #include<map>
 3 #include<string>
 4 #include<cstring>
 5 #include<cstdio>
 6 #include<cstdlib>
 7 #include<cmath>
 8 #include<queue>
 9 #include<vector>
10 #include<algorithm>
11 #include<cmath>
12 using namespace std;
13 int gcd(int a,int b){
14     if(b==0)  return a;
15     int r;
16     while((r=a%b)){
17         a=b;
18         b=r;
19     }
20     return b;
21 }
22 int main(){
23     int x1,y1,x2,y2,x3,y3;
24     while(cin>>x1>>y1>>x2>>y2>>x3>>y3&&(x1||y1||x2||y2||x3||y3)){
25         /*if(x1==0&&y1==0&&x2==0&&y2==0&&x3==0&&y3==0)
26         break;*/
27         int area=fabs(((x1-x2)*(y1-y3)-(x1-x3)*(y1-y2))*1.0/2);//叉乘可能为负 
28         //cout<<area<<endl;
29         int b=abs(gcd(x1-x2,y1-y2))+abs(gcd(x2-x3,y2-y3))+abs(gcd(x3-x1,y3-y1));//坐标平移，最大公约数+1就是边上的整点 
30         //cout<<b<<endl;
31         int pick=area-b/2+1;//pick公式 
32         cout<<pick<<endl;
33     } 
34     return 0;
35 }