1010 Area

题目要求面积和判断非相邻边不相交。和数学和几何有关系。

 #include <stdio.h>
 #include <math.h>

 #define MISS 0.0000001

 int det(double x1,double y1,double x2,double y2,double x3,double y3){
     double w1,w2;
     w1=x1*y2+x2*y3+x3*y1;
     w2=x2*y1+x3*y2+x1*y3;
     if(fabs(w1-w2)<MISS)
         ;
     else if(w1>w2)
             ;
         else if(w1<w2)
                 ;
 }

 int main(){
     ,temp;
     ],y[],area;
     while(scanf("%d",&n)&&n){
         count++;
         )
             printf("\n");
         printf("Figure %d: ",count);
         ;i<n;i++)
             scanf("%lf%lf",&x[i],&y[i]);
         ){
             printf("Impossible\n");
             continue;
         }
         ;i<n;i++){
             )/n;j<i-;j++){
                 temp=(i+)%n;
                 ],y[j+])*det(x[j],y[j],x[temp],y[temp],x[j+],y[j+])<=&&
                 det(x[i],y[i],x[j],y[j],x[temp],y[temp])*det(x[i],y[i],x[j+],y[j+],x[temp],y[temp])<=){
                     printf("Impossible\n");
                     goto quit;
                 }
             }
         }
         area=;
         ;i<n;i++)
             area+=x[i]*y[(i+)%n]-y[i]*x[(i+)%n];
         printf();
         quit:;
     }
     ;
 }