hdoj Clarke and five-pointed star 5563 （判断能否组成五角星）

Clarke and five-pointed star

Time Limit: 2000/1000 MS (Java/Others)    Memory Limit: 65536/65536 K (Java/Others)

Total Submission(s): 566    Accepted Submission(s): 298


[align=left]Problem Description[/align]
Clarke is a patient with multiple personality disorder. One day, Clarke turned into a learner of geometric.

When he did a research with polygons, he found he has to judge if the polygon is a five-pointed star at many times. There are 5 points on a plane, he wants to know if a five-pointed star existed with 5 points given.

[align=left]Input[/align]
The first line contains an integer
T(1≤T≤10),
the number of the test cases.

For each test case, 5 lines follow. Each line contains 2 real numbers
xi,yi(−109≤xi,yi≤109),
denoting the coordinate of this point.

[align=left]Output[/align]
Two numbers are equal if and only if the difference between them is less than
10−4.

For each test case, print Yes
if they can compose a five-pointed star. Otherwise, print
No.
(If 5 points are the same, print Yes.
)

[align=left]Sample Input[/align]

2
3.0000000 0.0000000
0.9270509 2.8531695
0.9270509 -2.8531695
-2.4270509 1.7633557
-2.4270509 -1.7633557
3.0000000 1.0000000
0.9270509 2.8531695
0.9270509 -2.8531695
-2.4270509 1.7633557
-2.4270509 -1.7633557

[align=left]Sample Output[/align]

Yes
No

Hint





[align=left]Source[/align]

#include<stdio.h>
#include<string.h>
#include<math.h>
#include<algorithm>
#define INF 0x3f3f3f3f
using namespace std;
double b[3100];
int map[310][310];
struct zz
{
double x;
double y;
}a[310];
int main()
{
int t,i,j;
scanf("%d",&t);
while(t--)
{
for(i=0;i<5;i++)
scanf("%lf%lf",&a[i].x,&a[i].y);
int k=0;
double mm=1.0*INF;
memset(map,0,sizeof(map));
for(i=0;i<5;i++)
{
for(j=i+1;j<5;j++)
{
if(map[i][j]||map[j][i])//消除重边
continue;
b[k]=(a[i].x-a[j].x)*(a[i].x-a[j].x)+(a[i].y-a[j].y)*(a[i].y-a[j].y);
mm=min(mm,b[k]);
k++;
map[i][j]=1;
}
}
int num=0;
for(i=0;i<k;i++)
if(b[i]-mm<=1e-4)
num++;
if(num==5)
printf("Yes\n");
else
printf("No\n");
}
return 0;
}