You are developing a software for painting rectangles on the screen. The software supports drawing several rectangles and filling some of them with a color different from the color of the background. You are to implement an important function. The function answer such queries as what is the colored area if a subset of rectangles on the screen are filled.
扫描线裸题
1 #include<stdio.h>
2 #include<string.h>
3 #include<algorithm>
4 #include<math.h>
5 using namespace std;
6 const int maxn=50;
7
8 int st[maxn<<2],cov[maxn<<2],y[maxn];
9 int Q[maxn];
10
11 struct rect{
12 int x1,y1,x2,y2;
13 }R[maxn];
14
15 struct seg{
16 int x,y1,y2,c;
17 bool operator < (const seg a)const{
18 return x<a.x;
19 }
20 }s[maxn];
21
22 inline void build(){
23 memset(st,0,sizeof(st));
24 memset(cov,0,sizeof(cov));
25 }
26
27 void pushup(int o,int l,int r){
28 if(cov[o])st[o]=y[r]-y[l];
29 else if(l+1==r)st[o]=0;
30 else st[o]=st[o<<1]+st[o<<1|1];
31 }
32
33 void update(int o,int l,int r,seg a){
34 if(a.y1<=y[l]&&a.y2>=y[r]){
35 cov[o]+=a.c;
36 pushup(o,l,r);
37 return;
38 }
39 if(l+1==r)return;
40 int m=l+((r-l)>>1);
41 if(a.y1<y[m])update(o<<1,l,m,a);
42 if(a.y2>y[m])update(o<<1|1,m,r,a);
43 pushup(o,l,r);
44 }
45
46 int main(){
47 int n,m,c=0;
48 while(scanf("%d%d",&n,&m)!=EOF&&n+m){
49 printf("Case %d:\n",++c);
50 for(int i=1;i<=n;++i)scanf("%d%d%d%d",&R[i].x1,&R[i].y1,&R[i].x2,&R[i].y2);
51 build();
52 for(int q=1;q<=m;++q){
53 int k;
54 scanf("%d",&k);
55 int cnt=0;
56 for(int i=1;i<=k;++i){
57 int num;
58 scanf("%d",&num);
59 ++cnt;
60 s[cnt].x=R[num].x1;s[cnt].y1=R[num].y1;s[cnt].y2=R[num].y2;
61 s[cnt].c=1;
62 y[cnt]=R[num].y1;
63 ++cnt;
64 s[cnt].x=R[num].x2;s[cnt].y1=R[num].y1;s[cnt].y2=R[num].y2;
65 s[cnt].c=-1;
66 y[cnt]=R[num].y2;
67 }
68 sort(y+1,y+cnt+1);
69 int t=unique(y+1,y+cnt+1)-(y+1);
70 sort(s+1,s+cnt+1);
71 int sum=0;
72 for(int j=1;j<cnt;++j){
73 update(1,1,t,s[j]);
74 sum+=st[1]*(s[j+1].x-s[j].x);
75 }
76 update(1,1,t,s[cnt]);
77 printf("Query %d: %d\n",q,sum);
78 }
79 printf("\n");
80 }
81 return 0;
82 }
