hdu2461 Rectangles 线段树--扫描线

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

 #include<stdio.h>
 #include<string.h>
 #include<algorithm>
 #include<math.h>
 using namespace std;
 const int maxn=;

 int st[maxn<<],cov[maxn<<],y[maxn];
 int Q[maxn];

 struct rect{
     int x1,y1,x2,y2;
 }R[maxn];

 struct seg{
     int x,y1,y2,c;
     bool operator < (const seg a)const{
         return x<a.x;
     }
 }s[maxn];

 inline void build(){
     memset(st,,sizeof(st));
     memset(cov,,sizeof(cov));
 }

 void pushup(int o,int l,int r){
     if(cov[o])st[o]=y[r]-y[l];
     else if(l+==r)st[o]=;
     else st[o]=st[o<<]+st[o<<|];
 }

 void update(int o,int l,int r,seg a){
     if(a.y1<=y[l]&&a.y2>=y[r]){
         cov[o]+=a.c;
         pushup(o,l,r);
         return;
     }
     if(l+==r)return;
     int m=l+((r-l)>>);
     if(a.y1<y[m])update(o<<,l,m,a);
     if(a.y2>y[m])update(o<<|,m,r,a);
     pushup(o,l,r);
 }

 int main(){
     int n,m,c=;
     while(scanf("%d%d",&n,&m)!=EOF&&n+m){
         printf("Case %d:\n",++c);
         for(int i=;i<=n;++i)scanf("%d%d%d%d",&R[i].x1,&R[i].y1,&R[i].x2,&R[i].y2);
         build();
         for(int q=;q<=m;++q){
             int k;
             scanf("%d",&k);
             int cnt=;
             for(int i=;i<=k;++i){
                 int num;
                 scanf("%d",&num);
                 ++cnt;
                 s[cnt].x=R[num].x1;s[cnt].y1=R[num].y1;s[cnt].y2=R[num].y2;
                 s[cnt].c=;
                 y[cnt]=R[num].y1;
                 ++cnt;
                 s[cnt].x=R[num].x2;s[cnt].y1=R[num].y1;s[cnt].y2=R[num].y2;
                 s[cnt].c=-;
                 y[cnt]=R[num].y2;
             }
             sort(y+,y+cnt+);
             int t=unique(y+,y+cnt+)-(y+);
             sort(s+,s+cnt+);
             int sum=;
             for(int j=;j<cnt;++j){
                 update(,,t,s[j]);
                 sum+=st[]*(s[j+].x-s[j].x);
             }
             update(,,t,s[cnt]);
             printf("Query %d: %d\n",q,sum);
         }
         printf("\n");
     }
     return ;
 }