B - Atlantis

#include <stdio.h>
#include <iostream>
#include <algorithm>

using namespace std;
struct node
{
    int l,r;
    int c;
    double cnt,lf,rf;
}seg[603];
double y[201];
struct Line
{
    double x,y1,y2;
    int f;
}line[201];
bool cmp(Line a,Line b)
{
    return a.x<b.x;
}
void Build(int t,int l,int r)
{
    seg[t].l = l;
    seg[t].r = r;
    seg[t].cnt = seg[t].c = 0;
    seg[t].lf = y[l];
    seg[t].rf = y[r];
    if(l + 1 == r)
    return ;
    int mid = (l + r)/2;
    Build(2*t,l,mid);
    Build(2*t+1,mid,r);
}
void calen(int t)
{
    if(seg[t].c>0)
    {
        seg[t].cnt = seg[t].rf-seg[t].lf;
        return ;
    }
    if(seg[t].l+1 == seg[t].r)seg[t].cnt = 0;
    else seg[t].cnt = seg[2 *t].cnt+seg[2 *t+1].cnt;

}
void update(int t,Line e)
{
    if(e.y1 == seg[t].lf && e.y2 == seg[t].rf)
    {
        seg[t].c+=e.f;
        calen(t);
        return ;
    }
    if(e.y2<=seg[2 *t].rf)update(2 *t,e);
    else if(e.y1>=seg[2 * t+1].lf)update(2 *t+1,e);
    else
    {
        Line tmp = e;
        tmp.y2 = seg[2 *t].rf;
        update(2 * t,tmp);
        tmp = e;
        tmp.y1 = seg[t<<1|1].lf;
        update(2 * t + 1,tmp);
    }
    calen(t);
}
int main()
{
    int i,n,t,iCase = 0;
    double x1,y1,x2,y2;
    while(scanf("%d",&n),n)
    {
        iCase++;
        t = 1;
        for(i = 1;i<=n;i++)
        {
            scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
            line[t].x = x1;
            line[t].y1 = y1;
            line[t].y2 = y2;
            line[t].f = 1;
            y[t] = y1;
            t++;
            line[t].x = x2;
            line[t].y1 = y1;
            line[t].y2 = y2;
            line[t].f = -1;
            y[t] = y2;
            t++;
         }
         sort(line+1,line+t,cmp);
         sort(y+1,y+t);
         Build(1,1,t-1);
         update(1,line[1]);
         double res = 0;
         for(i = 2;i<t;i++)
         {
             res+=seg[1].cnt*(line[i].x - line[i-1].x);
             update(1,line[i]);
         }
         printf("Test case #%d\nTotal explored area: %.2f\n\n",iCase,res);
    }
    return 0;
}

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