poj 1066

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判读线段相交。。又是一道练手题。。

不过判断线段相交那里<=EPS会WA,<=-EPS就会AC

简直无法直视了。。。

#include<iostream>#include<cstdio>#include<cstring>#include<cmath>#include<vector>#include<queue>#include<algorithm>using namespace std;const double EPS=1e-11;double add(double a,double b){    if(abs(a+b)<EPS*(abs(a)+abs(b)))    return 0;    return a+b;}struct P{    double x,y;    P(){}    P(double x,double y):x(x),y(y){    }    P operator +(P p){        return P(add(x,p.x),add(y,p.y));    }    P operator -(P p){        return P(add(x,-p.x),add(y,-p.y));    }    P operator *(double d){        return P(x*d,y*d);    }    double det(P p){        return add(x*p.y,-y*p.x);    }    double dot(P p){        return add(x*p.x,y*p.y);    }};P q[100005],p[100005],r[100];int ans[1000005];bool judge(int a,int b){    if(((q[b]-r[0]).det(r[a]-r[0])*(p[b]-r[0]).det(r[a]-r[0]))<=-EPS)    {        if(((r[0]-q[b]).det(p[b]-q[b])*(r[a]-q[b]).det(p[b]-q[b]))<=-EPS)        return 1;        return 0;    }    return 0;}int main(){    int n;    while(~scanf("%d",&n))    {        for(int i=0;i<n;i++)        scanf("%lf%lf%lf%lf",&q[i].x,&q[i].y,&p[i].x,&p[i].y);        scanf("%lf%lf",&r[0].x,&r[0].y);        if(n==0)        {            printf("Number of doors = 1\n");            continue;        }int l=1;for(double i=1.0;i<=99.0;i++){    for(int j=0;j<n;j++)    {    r[l].x=0.0;    r[l].y=i;    l++;    r[l].x=100.0;    r[l].y=i;    l++;    r[l].y=0.0;    r[l].x=i;    l++;    r[l].y=100.0;    r[l].x=i;    l++;    }}        int mn=100000;        for(int i=1;i<l;i++)        {            int ans=0;            for(int j=0;j<n;j++)            {                if(judge(i,j))                ans++;            }            if(ans<mn)            mn=ans;        }        printf("Number of doors = %d\n",mn+1);    }    return 0;}

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