www.pudn.com > zhejiang_university_acm_onlinejudge_code.rar > zp1010_p.cpp

#define cin fin 
#include  
#include  
#include  
#include  
 
#define eps 1e-8 
 
double x[1001],y[1001]; 
 
double area(int n, double x[], double y[]) 
{ 
  int i; 
  double ans = 0; 
  for(i=1; i<=n; i++) 
    ans += x[i]*y[i-1]-y[i]*x[i-1]; 
  return fabs(ans/2); 
} 
double cross(int a,int b,int c) 
{ 
  return (x[b]-x[a])*(y[c]-y[a])-(y[b]-y[a])*(x[c]-x[a]); 
} 
double dot(int a,int b,int c) 
{ 
  return (x[b]-x[a])*(x[c]-x[a])+(y[b]-y[a])*(y[c]-y[a]); 
} 
int dblcmp(double d) 
{ 
  if(fabs(d)0)?1:-1; 
} 
int between(int a, int b, int c) //a is between b->c 
{ 
  return dblcmp(dot(a,b,c)); 
} 
int intersect(int s, int t) 
{ 
  int d1,d2,d3,d4; 
  d1 = dblcmp(cross(s,s+1,t)); 
  d2 = dblcmp(cross(s,s+1,t+1)); 
  d3 = dblcmp(cross(t,t+1,s)); 
  d4 = dblcmp(cross(t,t+1,s+1)); 
  if(d1*d2<0 && d3*d4<0) 
    return 1; 
  if (d1==0 && between(t,s,s+1)<=0 || 
      d2==0 && between(t+1,s,s+1)<=0 || 
      d3==0 && between(s,t,t+1)<=0 || 
      d4==0 && between(s+1,t,t+1)<=0) 
    return 2; 
  return 0; 
} 
int main() 
{ 
  fstream fin("d:\in1010.txt"); 
  int n,i,j,ncase=0; 
  while(cin>>n && n) 
  { 
    for(i=1; i<=n; i++) 
      cin>>x[i]>>y[i]; 
    x[0]=x[n]; y[0]=y[n]; 
    if (ncase) 
      cout<1; i--) 
      if(intersect(0,i)) 
      { 
        flag = 0; 
        goto output; 
      } 
    for(i=n-3; i>0; i--) 
      for(j=i+2; j