hdu 1542 线段树 求面积并

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
#define lson l,m,rt<<1
#define rson m+1,r,rt<<1|1
const int maxn  =  1000;
double sum[maxn<<2];
int cover[maxn<<2];
double  x[maxn];
struct seg{
    double l,r,h;
    int flag;
    seg(){}
    seg(double _l,double _r,double _h,int _flag):l(_l),r(_r),h(_h),flag(_flag){}
    bool operator <(const seg &cmp) const {
        return h<cmp.h;
    }
}horizontal_seg[maxn];
void pushup(int rt,int l,int r)
{
     if(cover[rt]){
         sum[rt]=x[r+1]-x[l];
     }
     else if(l==r){
         sum[rt]=0;
     }
     else sum[rt]=sum[rt<<1]+sum[rt<<1|1];
}
void update(int L,int R,int c,int l,int r,int rt)
{
     if(L<=l&&r<=R){
         cover[rt]+=c;
         pushup(rt,l,r);
         return ;
     }
     int m=(l+r)>>1;
     if(L<=m) update(L,R,c,lson);
     if(R>m) update(L,R,c,rson);
     pushup(rt,l,r);
}
int bin(double key,int n,double x[]){
    int l=0,r=n-1,mid,best=-1;
    while(l<=r){
        mid=(l+r)>>1;
        if(x[mid]<=key){
            best=mid;
            l=mid+1;
        }
        else r=mid-1;
    }
    return best;
}
int main()
{
    int n,i,j,tot,cases=1;
    double x1,y1,x2,y2;
    while(scanf("%d",&n),n)
    {
        tot=0;
        for(i=1;i<=n;i++)
        {
            scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
            x[tot]=x1;
            horizontal_seg[tot++]=seg(x1,x2,y1,1);
            x[tot]=x2;
            horizontal_seg[tot++]=seg(x1,x2,y2,-1);
        }
        sort(x,x+tot);
        sort(horizontal_seg,horizontal_seg+tot);
        for(i=1,j=1;i<tot;i++){
            if(x[i]!=x[i-1]) x[j++]=x[i];
        }
       memset(cover , 0 , sizeof(cover));
       memset(sum , 0 , sizeof(sum));
        double area=0;
        for(i=0;i<tot-1;i++)
        {
            int left=bin(horizontal_seg[i].l,j,x);
            int right=bin(horizontal_seg[i].r,j,x)-1;
            update(left,right,horizontal_seg[i].flag,0,j-1,1);
            area+=sum[1]*(horizontal_seg[i+1].h-horizontal_seg[i].h);
        }
        printf("Test case #%d\n",cases++);
        printf("Total explored area: %.2lf\n\n",area);
    }
    return 0;
}