矩形面积并 (hdu1542)

标签：算法   计算几何   

#include <iostream>
#include<string>
#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
const int mmax = 210;
const double eps = 1e-8;
int sgn(double x)
{
    if(fabs(x)<eps)
        return 0;
    return x<0?-1:1;
}
struct Rect
{
    double x1,x2;
    double y1,y2;
    void read()
    {
        scanf("%lf %lf %lf %lf",&x1,&y1,&x2,&y2);
        if(x1>x2)
            swap(x1,x2);
        if(y1>y2)
            swap(y1,y2);
    }
}R[110];
struct node
{
    int l,r;
    int cov;
    double len;
    int mid()
    {
        return (l+r)>>1;
    }
}T[4*mmax];
struct Num
{
    double x;
    int id;
    bool operator < (const Num &a) const
    {
        return x<a.x;
    }
}X[mmax];
struct Line
{
    int l,r;
    double y;
    int fg;
    bool operator < (const Line &a) const
    {
        return y<a.y;
    }
}L[mmax];
void build(int id,int l,int r)
{
    T[id].l=l,T[id].r=r;
    T[id].cov=0,T[id].len=0;
    if(l==r)
        return ;
    int mid=T[id].mid();
    build(id<<1,l,mid);
    build(id<<1|1,mid+1,r);
}
double pos[mmax];
void updata(int id,int l,int r,int fg)
{
    if(l<=T[id].l && T[id].r<=r)
    {
        T[id].cov+=fg;
        if(T[id].cov)
            T[id].len=pos[T[id].r+1]-pos[T[id].l];
        else
        {
            if(T[id].l==T[id].r)
                T[id].len=0;
            else
                T[id].len=T[id<<1].len+T[id<<1|1].len;
        }
        return ;
    }
    int mid=T[id].mid();
    if(mid>=l)
        updata(id<<1,l,r,fg);
    if(mid<r)
        updata(id<<1|1,l,r,fg);
    if(T[id].cov==0)
    {
        T[id].len=T[id<<1].len+T[id<<1|1].len;
    }
}
int id[mmax];
int main()
{
    int n,ca=0;
    while(~scanf("%d",&n)&&n)
    {
        int cnt=0;
        for(int i=0;i<n;i++)
        {
            R[i].read();
            X[cnt].x=R[i].x1;
            X[cnt].id=cnt;
            cnt++;
            X[cnt].x=R[i].x2;
            X[cnt].id=cnt;
            cnt++;
        }

        sort(X,X+cnt);
        id[0]=1;
        pos[1]=X[0].x;
        for(int i=1;i<cnt;i++)
        {
            if(sgn(X[i].x-X[i-1].x)==0)
                id[X[i].id]=id[X[i-1].id];
            else
                id[X[i].id]=id[X[i-1].id]+1;
            pos[id[X[i].id]]=X[i].x;
        }
        for(int i=0;i<n;i++)
        {
            L[i].l=id[2*i];
            L[i].r=id[2*i+1];
            L[i].y=R[i].y1;
            L[i].fg=1;
            L[i+n].l=id[2*i];
            L[i+n].r=id[2*i+1];
            L[i+n].y=R[i].y2;
            L[i+n].fg=-1;
        }
        sort(L,L+2*n);
        build(1,1,id[X[cnt-1].id]-1);
        updata(1,L[0].l,L[0].r-1,L[0].fg);
        double ans=0.0;
        for(int i=1;i<2*n;i++)
        {
            ans+=(L[i].y-L[i-1].y)*T[1].len;
            updata(1,L[i].l,L[i].r-1,L[i].fg);
        }
        printf("Test case #%d\nTotal explored area: %.2lf\n\n",++ca,ans);
    }

    return 0;
}

矩形面积并 (hdu1542)

标签：算法   计算几何   

原文地址：http://blog.csdn.net/u012127882/article/details/46367835