poj1151——Atlantis

题意：求轮廓面积。

思路：离散化+线段树。和求周长一样的思路。

#include<cstdio> #include<iostream> #include<string> #include<algorithm> using namespace std; #define maxn 120 int n,cnt; double INDEX[maxn*3];//存y class line { public: double st,ed; double x; bool inout; bool operator<(line o)const { return x<o.x ; } }; class stnode { public: int l,r; double len; int segnum; int cover; double sum; bool lcover,rcover; stnode() { l=r=0; len=segnum=cover=sum=0; lcover=rcover=false; } }; stnode st[maxn*8]; line yline[maxn*3]; void build(int l,int r,int index) { st[index].l =l; st[index].r =r; st[index].len =INDEX[r]-INDEX[l]; st[index].cover =0; st[index].segnum =0; st[index].sum=0; st[index].lcover =st[index].rcover =false; if(r-l>1) { int mid=(l+r)>>1; build(l,mid,index*2); build(mid,r,index*2+1); } } int getindex(double y) { return lower_bound(INDEX,INDEX+cnt,y)-INDEX; } void getlen(int index) { if(st[index].cover >0) st[index].sum=st[index].len ; else if(st[index].r -st[index].l >1) st[index].sum =st[index*2].sum +st[index*2+1].sum ; else st[index].sum =0; } void getsegnum(int index) { if(st[index].cover >0) { st[index].lcover =st[index].rcover =true; st[index].segnum =1; } else if(st[index].r -st[index].l >1) { st[index].lcover =st[index*2].lcover ; st[index].rcover =st[index*2+1].rcover ; st[index].segnum =st[index*2].segnum +st[index*2+1].segnum -st[index*2].rcover *st[index*2+1].lcover ; } else { st[index].lcover =st[index].rcover =false; st[index].segnum =0; } } void Insert(int l,int r,int index) { if(st[index].l ==l&&st[index].r ==r) st[index].cover ++; else { int mid=(st[index].l+st[index].r )>>1; if(l>=mid) Insert(l,r,index*2+1); else if(r<=mid) Insert(l,r,index*2); else { Insert(l,mid,index*2); Insert(mid,r,index*2+1); } } getlen(index); getsegnum(index); } void Delete(int l,int r,int index) { if(st[index].l==l&&st[index].r ==r) st[index].cover --; else { int mid=(st[index].l +st[index].r )>>1; if(r<=mid) Delete(l,r,index*2); else if(l>=mid) Delete(l,r,index*2+1); else { Delete(l,mid,index*2); Delete(mid,r,index*2+1); } } getlen(index); getsegnum(index); } int main() { double x1,y1,x2,y2; int i,j,k,ca=1; while(1) { cin>>n; if(n==0) break; for(i=0;i<n;i++) { cin>>x1>>y1>>x2>>y2; yline[i*2].x=x1;yline[i*2].st =y1;yline[i*2].ed =y2; yline[i*2].inout =true; yline[i*2+1].x=x2;yline[i*2+1].st =y1;yline[i*2+1].ed =y2; yline[i*2+1].inout =false; INDEX[i*2]=y1; INDEX[i*2+1]=y2; } sort(INDEX,INDEX+n*2); sort(yline,yline+n*2); cnt=0; for(i=1;i<n*2;i++) { if(INDEX[i]!=INDEX[i-1]) INDEX[cnt++]=INDEX[i-1]; } INDEX[cnt++]=INDEX[2*n-1]; build(0,cnt-1,1); double ans=0; double lsum=0; for(i=0;i<2*n-1;i++) { if(yline[i].inout ) Insert(getindex(yline[i].st ),getindex(yline[i].ed ),1); else Delete(getindex(yline[i].st ),getindex(yline[i].ed ),1); ans+=1.0*st[1].sum*(yline[i+1].x-yline[i].x ) ; } printf("Test case #%d\n",ca++); printf("Total explored area: %.2lf\n",ans); printf("\n"); } return 0; }