HDU 5365 Run

因为给出的点都是整数，都在网格上的，所以正三角形，正五边形，正六边形都是不存在的。

暴力枚举四个点，判断一下是不是正方形即可。

#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
using namespace std;

int n;
int x[30],y[30];


class Coordinate
{
public:
    double xCoordinate;
    double yCoordinate;

    Coordinate(double x = 0,double y = 0)
    {
        this->xCoordinate = x;
        this->yCoordinate = y;
    }

    bool operator!=(Coordinate const &comp) const
    {
        return (this->xCoordinate != comp.xCoordinate ||
                this->yCoordinate != comp.yCoordinate);
    }
}array[10];


bool Judge(Coordinate const x,Coordinate const y,Coordinate const z)
{
    Coordinate *mVector = new Coordinate(x.xCoordinate - y.xCoordinate,
                                        x.yCoordinate - y.yCoordinate);
    Coordinate *nVector = new Coordinate(z.xCoordinate -
                                        (x.xCoordinate + y.xCoordinate)/2,
                                         z.yCoordinate -
                                         (x.yCoordinate + y.yCoordinate)/2);
    
    bool result = ((mVector->xCoordinate * nVector->xCoordinate +
                    mVector->yCoordinate * nVector->yCoordinate) == 0);

    if(result)
        result = (mVector->xCoordinate * mVector->xCoordinate +
                mVector->yCoordinate * mVector->yCoordinate)
                 == ((nVector->xCoordinate * nVector->xCoordinate +
                    nVector->yCoordinate * nVector->yCoordinate) * 4);

    delete mVector;
    delete nVector;

    return result;
}


bool IsSquare(Coordinate *array,int length)
{
    if(length != 4)
        return false;
    int a,b,c;

    if(Judge(array[0],array[1],array[2]))
    {
        a = 0;
        b = 1;
        c = 2;
    }
    else if(Judge(array[0],array[2],array[1]))
    {
        a = 0;
        b = 2;
        c = 1;
    }
    else if(Judge(array[2],array[1],array[0]))
    {
        a = 1;
        b = 2;
        c = 0;
    }
    else
        return false;

    return (array[3] != array[c] && Judge(array[a],array[b],array[3]));
}

int main()
{
    while(~scanf("%d",&n)){
    int ans=0;
    for(int i=0;i<n;i++)
        scanf("%d%d",&x[i],&y[i]);
    for(int a=0;a<n;a++)
        for(int b=a+1;b<n;b++)
            for(int c=b+1;c<n;c++)
                for(int d=c+1;d<n;d++)
                {
                    array[0].xCoordinate=x[a];array[0].yCoordinate=y[a];
                    array[1].xCoordinate=x[b];array[1].yCoordinate=y[b];
                    array[2].xCoordinate=x[c];array[2].yCoordinate=y[c];
                    array[3].xCoordinate=x[d];array[3].yCoordinate=y[d];
                    if(IsSquare(array,4)) ans++;
                }
    printf("%d
",ans);
    }
    return 0;
}