ZOJ1010 Area
2010-10-01 12:05
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#include<iostream>
#include<iomanip>
using namespace std;
#define min(x,y) (x<y?x:y)
#define max(x,y) (x>y?x:y)
struct point{
double x;
double y;
};
struct line{
point a;
point b;
};
point points[1010];
line lines[1010];
double multi(point p1,point p2,point p0)
{
return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);
}
bool intersect(line u,line v)
{
return ((max(u.a.x,u.b.x)>=min(v.a.x,v.b.x))&&
(max(v.a.x,v.b.x)>=min(u.a.x,u.b.x))&&
(max(u.a.y,u.b.y)>=min(v.a.y,v.b.y))&&
(max(v.a.y,v.b.y)>=min(u.a.y,u.b.y))&&
(multi(v.a,u.b,u.a)*multi(u.b,v.b,u.a)>=0)&&
(multi(u.a,v.b,v.a)*multi(v.b,u.b,v.a)>=0));
}
double polygonarea(int n)
{
double area=0.0;
for(int i=0;i<n;i++){
int j=(i+1)%n;
area+=(points[i].x * points[j].y)-(points[i].y * points[j].x);
}
area/=2;
return (area<0? -area:area);
}
int main()
{
int cases;
int num;
int i,j;
double result=0.0;
cases=0;
while(cin>>num && num!=0){
cases++;
if(cases>1)
cout<<endl;
for(i=0;i<num;i++){
cin>>points[i].x>>points[i].y;
}
if(num<3){
cout<<"Figure "<<cases<<": Impossible"<<endl;
continue;
}
for(i=0;i<num;i++){
lines[i].a=points[i];
lines[i].b=points[(i+1)%num];
}
bool flag=false;
for(i=0;i<num;i++){
for(j=0;j<num;j++) {
if(j!=(i+1)%num && j!=(i-1+num)%num && j!=i){
flag=intersect(lines[i],lines[j]);
if(flag==true)
{
goto L;
}
}
}
}
result= polygonarea(num);
cout<<"Figure "<<cases<<": "<<setprecision(2)<<fixed<<result<<endl;
continue;
L: cout<<"Figure "<<cases<<": Impossible"<<endl;
}
return 0;
}
#include<iomanip>
using namespace std;
#define min(x,y) (x<y?x:y)
#define max(x,y) (x>y?x:y)
struct point{
double x;
double y;
};
struct line{
point a;
point b;
};
point points[1010];
line lines[1010];
double multi(point p1,point p2,point p0)
{
return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);
}
bool intersect(line u,line v)
{
return ((max(u.a.x,u.b.x)>=min(v.a.x,v.b.x))&&
(max(v.a.x,v.b.x)>=min(u.a.x,u.b.x))&&
(max(u.a.y,u.b.y)>=min(v.a.y,v.b.y))&&
(max(v.a.y,v.b.y)>=min(u.a.y,u.b.y))&&
(multi(v.a,u.b,u.a)*multi(u.b,v.b,u.a)>=0)&&
(multi(u.a,v.b,v.a)*multi(v.b,u.b,v.a)>=0));
}
double polygonarea(int n)
{
double area=0.0;
for(int i=0;i<n;i++){
int j=(i+1)%n;
area+=(points[i].x * points[j].y)-(points[i].y * points[j].x);
}
area/=2;
return (area<0? -area:area);
}
int main()
{
int cases;
int num;
int i,j;
double result=0.0;
cases=0;
while(cin>>num && num!=0){
cases++;
if(cases>1)
cout<<endl;
for(i=0;i<num;i++){
cin>>points[i].x>>points[i].y;
}
if(num<3){
cout<<"Figure "<<cases<<": Impossible"<<endl;
continue;
}
for(i=0;i<num;i++){
lines[i].a=points[i];
lines[i].b=points[(i+1)%num];
}
bool flag=false;
for(i=0;i<num;i++){
for(j=0;j<num;j++) {
if(j!=(i+1)%num && j!=(i-1+num)%num && j!=i){
flag=intersect(lines[i],lines[j]);
if(flag==true)
{
goto L;
}
}
}
}
result= polygonarea(num);
cout<<"Figure "<<cases<<": "<<setprecision(2)<<fixed<<result<<endl;
continue;
L: cout<<"Figure "<<cases<<": Impossible"<<endl;
}
return 0;
}
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