1 #include<stdio.h>
2 #include<string.h>
3 #include<algorithm>
4 using namespace std;
5 struct LINE
6 {
7 double x,ydown,yup;
8 int flag;
9 bool operator<(const LINE &a) const
10 {
11 return x<a.x;
12 }
13 }line[1005];
14 int cover[1005],ff;
15 double prex[1005],downy[1005],upy[1005],xx,y1,y2,y[1005];
16 void build(int o,int l,int r)
17 {
18 prex[o]=0.0; cover[o]=0;
19 downy[o]=y[l]; upy[o]=y[r];
20 if (l+1==r) return;
21 int mid=l+(r-l)/2;
22 build(o*2,l,mid);
23 build(o*2+1,mid,r);
24 }
25 double update(int o,int l,int r)
26 {
27 int mid=l+(r-l)/2;
28 double temp;
29 if (l+1==r)
30 {
31 if (cover[o]>=1)
32 {
33 cover[o]+=ff; temp=prex[o]; prex[o]=xx;
34 return (upy[o]-downy[o])*(xx-temp);
35 }
36 else{cover[o]+=ff; prex[o]=xx; return 0.0; }
37 }
38 if (y1>=upy[o*2]) return update(o*2+1,mid,r);
39 if (y2<=downy[o*2+1]) return update(o*2,l,mid);
40 return update(o*2,l,mid)+update(o*2+1,mid,r);
41 }
42 int main()
43 {
44 int t=0,num,i,n;
45 double x1,x2;
46 while (~scanf("%d",&n)&&n)
47 {
48 num=0;
49 for (i=1;i<=n;i++)
50 {
51 scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
52 num++; y[num]=y1;
53 line[num].x=x1; line[num].ydown=y1; line[num].yup=y2; line[num].flag=1;
54 num++; y[num]=y2;
55 line[num].x=x2; line[num].ydown=y1; line[num].yup=y2; line[num].flag=-1;
56 }
57 sort(y+1,y+num+1);
58 sort(line+1,line+num+1);
59 build(1,1,num);
60 double ans=0.0;
61 for (i=1;i<=num;i++)
62 {
63 y1=line[i].ydown; y2=line[i].yup;
64 xx=line[i].x; ff=line[i].flag;
65 ans+=update(1,1,num);
66 }
67 printf("Test case #%d\n",++t);
68 printf("Total explored area: %0.2lf\n\n",ans);
69 }
70 }
http://acm.hdu.edu.cn/showproblem.php?pid=1542
