(中等) HDU 1542 Atlantis，扫描线。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath>

#define lson L,M,lc
#define rson M+1,R,rc
#define lc po*2
#define rc po*2+1

using namespace std;

struct BIAN
{
    double x,y1,y2;
    int state;
};

BIAN bian[210];
double hash[210];
double BIT[210*4];
int COL[210*4];
int COU;

bool cmp(BIAN a,BIAN b)
{
    return a.x<b.x;
}

int find(double x)
{
    int L=1,R=COU;
    int M;

    while(R>L)
    {
        M=(L+R)/2;

        if(fabs(hash[M]-x)<0.000001)
            return M;

        if(hash[M]<x)
            L=M+1;
        else
            R=M-1;
    }

    return L;
}

void pushUP(int L,int R,int po)
{
    if(COL[po])
        BIT[po]=hash[R+1]-hash[L];
    else if(L==R)
        BIT[po]=0;
    else
        BIT[po]=BIT[lc]+BIT[rc];
}

void update(int ul,int ur,int ut,int L,int R,int po)
{
    if(ul<=L&&ur>=R)
    {
        COL[po]+=ut;

        if(COL[po]>0)
            BIT[po]=hash[R+1]-hash[L];
        else if(L==R)
            BIT[po]=0;
        else
            pushUP(L,R,po);

        return;
    }

    int M=(L+R)/2;

    if(ul<=M)
        update(ul,ur,ut,lson);
    if(ur>M)
        update(ul,ur,ut,rson);

    pushUP(L,R,po);
}

int main()
{
    int cas=0;
    int N;
    double x1,x2,y1,y2;
    double ans;

    for(cin>>N;N;cin>>N)
    {
        ans=0;
        COU=1;
        memset(hash,0,sizeof(hash));
        memset(COL,0,sizeof(COL));
        memset(BIT,0,sizeof(BIT));

        for(int i=1;i<=N;++i)
        {
            scanf("%lf %lf %lf %lf",&x1,&y1,&x2,&y2);

            bian[i*2-1].x=x1;
            bian[i*2-1].y1=y1;
            bian[i*2-1].y2=y2;
            bian[i*2-1].state=1;

            bian[i*2].x=x2;
            bian[i*2].y1=y1;
            bian[i*2].y2=y2;
            bian[i*2].state=-1;

            hash[COU++]=y1;
            hash[COU++]=y2;
        }

        sort(hash+1,hash+COU);
        sort(bian+1,bian+2*N+1,cmp);

        int k=2;
        for(int i=2;i<COU;++i)
            if(hash[i]!=hash[i-1])
                hash[k++]=hash[i];
        COU=k-1;

        for(int i=1;i<=2*N;++i)
        {
            ans+=BIT[1]*(bian[i].x-bian[i-1].x);

            update(find(bian[i].y1),find(bian[i].y2)-1,bian[i].state,1,COU-1,1);
        }

        ans+=BIT[1];
        printf("Test case #%d\nTotal explored area: %.2f\n\n",++cas,ans);
    }

    return 0;
}