Area Pick定理加叉积三角剖分

/*注意由于叉积的有向面积，进行剖分累加的时候一定要在最后取绝对值。不能在中间过程取。否则和会变大。*/#include <iostream>#include <stdio.h>#include <cmath>#define sum(a,b,c)  ((b.x-a.x)*(c.y-a.y)-(b.y-a.y)*(c.x-a.x))using namespace std;struct po{    int x,y;} point[105];int gcd(int n,int m){    if(m==0||n==0) return fabs(m-n);    else if(n%m==0) return m;    else return gcd(m,n%m);}int main(){    int t;    scanf("%d",&t);    for(int k=1; k<=t; k++)    {        int n;        int count=0;        scanf("%d",&n);        point[1].x=point[1].y=0;        for(int j=2; j<=n+1; j++)        {            scanf("%d %d",&point[j].x,&point[j].y);            point[j].x=point[j].x+point[j-1].x;            point[j].y=point[j].y+point[j-1].y;        }        for(int i=2; i<=n+1; i++)            count+=gcd(fabs(point[i].x-point[i-1].x),fabs(point[i].y-point[i-1].y));        count+=gcd(fabs(point[n+1].x-point[1].x),fabs(point[1].y-point[n+1].y));        double summ=0;        for(int i=2; i<=n; i++)            summ+=sum(point[1],point[i],point[i+1]);        summ=summ/2;        int ge=summ+1-count/2;        printf("Scenario #%d:\n",k);        printf("%d %d %.1lf\n",ge,count,summ);        printf("\n");    }    return 0;}