zoj 3720

为什么注释掉的地方是错的？  自己的代码好糟烂.....

直接枚举点  判是否在多边形内  加起来求概率    求面积的时候代码写搓了....     比不过别人两行的代码    而且到现在还找不到错.....

#include <iostream>
#include <fstream>
#include <cstring>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#define eps 1e-8
#define _sign(x) ((x)>eps?1:((x)<-eps?2:0))
#define zero(x) (((x)>0?(x):-(x))<eps)
#define offset 500
using namespace std;
const int N = 100;
struct point
{
    double x, y;
    point(double i, double j)
    {
        x = i, y = j;
    }
    point() {}
} p[N];

double xmult(point p1,point p2,point p0)
{
    return (p1.x-p0.x)*(p2.y-p0.y)-(p2.x-p0.x)*(p1.y-p0.y);
}
int inside(point q, int n, point *p)
{
    int s[3] = {1, 1, 1};
    for(int i = 0; i < n && s[1]|s[2]; i++)
        s[_sign(xmult(p[(i+1)%n], q, p[i]))] = 0;
    return s[1]|s[2];
}
int inside_polygon(point q,int n,point* p)
{
    point q2;
    int i=0,count;
    while (i<n)
        for (count=i=0,q2.x=rand()+offset,q2.y=rand()+offset; i<n; i++)
        {
            if (zero(xmult(q,p[i],p[(i+1)%n]))&&(p[i].x-q.x)*(p[(i+1)%n].x-q.x)<eps
                    &&(p[i].y-q.y)*(p[(i+1)%n].y-q.y)<eps)
                return 1;
            else if (zero(xmult(q,q2,p[i])))
                break;
            else if (xmult(q,p[i],q2)*xmult(q,p[(i+1)%n],q2)<-eps&&
                     xmult(p[i],q,p[(i+1)%n])*xmult(p[i],q2,p[(i+1)%n])<-eps)
                count++;
        }
    return count&1;
}
int main(void)
{
    double x0,y0,xn,yn;
    int a,b,n;
    while(scanf("%lf%lf%lf%lf",&x0,&y0,&xn,&yn) == 4)
    {
        int _x0 = ceil(x0), _y0 = ceil(y0), _xn = floor(xn), _yn = floor(yn);
//        printf("%d %d %d %d",_x0, _y0, _xn, _yn);
        scanf("%d%d%d",&n,&a,&b);
        for(int i = 0; i < n; i++)
        {
            scanf("%lf%lf",&p[i].x,&p[i].y);
        }
        double sum = 0;
        for(int i = _x0; i <= _xn; i++)
            for(int j = _y0; j <= _yn; j++)
            {
                if(inside_polygon(point(i, j), n, p))
                {
                    double r=(min(i+0.5,xn)-max(i-0.5,x0))*(min(j+0.5,yn)-max(j-0.5,y0));
                    sum += r*(i*a+j*b);
//                    if(i > _x0 && i < _xn && j > _y0 && j < _yn)
//                        sum += (i*a+j*b);
//                    else if(i > _x0 && i < _xn && (j == _y0 || j == _yn))
//                    {
//                        if(j == _y0)
//                            sum += (i*a+j*b)*((double)((double)_y0-y0+0.5));
//                        else
//                            sum += (i*a+j*b)*((yn-(double)_yn+0.5));
//                    }
//                    else if((i == _x0 || i == _xn) && j > _y0 && j < _yn)
//                    {
//                        if(i == _x0)
//                            sum += (i*a+j*b)*(((double)_x0-x0+0.5));
//                        else
//                            sum += (i*a+j*b)*((xn-(double)_xn+0.5));
//                    }
//                    else
//                    {
//                        if(i == _x0 && j == _y0)
//                            sum += (i*a+j*b)*(((double)_x0-x0+0.5))*(((double)_y0-y0+0.5));
//                        else if(i == _x0 && j == _yn)
//                            sum += (i*a+j*b)*(((double)_x0-x0+0.5))*((yn-(double)_yn+0.5));
//                        else if(i == _xn && j == _y0)
//                            sum += (i*a+j*b)*((xn-(double)_xn+0.5))*(((double)_y0-y0+0.5));
//                        else
//                            sum += (i*a+j*b)*((xn-(double)_xn+0.5))*((yn-(double)_yn+0.5));
//                    }
                }
            }
        printf("%.3lf\n",(double)sum/(xn-x0)/(yn-y0));
    }
    return 0;
}