poj 2954 Triangle

pick公式+gcd公式

 #include<iostream>
 #include<map>
 #include<string>
 #include<cstring>
 #include<cstdio>
 #include<cstdlib>
 #include<cmath>
 #include<queue>
 #include<vector>
 #include<algorithm>
 #include<cmath>
 using namespace std;
 int gcd(int a,int b){
     if(b==)  return a;
     int r;
     while((r=a%b)){
         a=b;
         b=r;
     }
     return b;
 }
 int main(){
     int x1,y1,x2,y2,x3,y3;
     while(cin>>x1>>y1>>x2>>y2>>x3>>y3&&(x1||y1||x2||y2||x3||y3)){
         /*if(x1==0&&y1==0&&x2==0&&y2==0&&x3==0&&y3==0)
         break;*/
         int area=fabs(((x1-x2)*(y1-y3)-(x1-x3)*(y1-y2))*1.0/);//叉乘可能为负
         //cout<<area<<endl;
         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
         //cout<<b<<endl;
         int pick=area-b/+;//pick公式
         cout<<pick<<endl;
     }
     return ;
 }