POJ 1389 Area of Simple Polygons .

题目地址：http://poj.org/problem?id=1389

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
const int maxn=1000+5;
int y[maxn],nNode;
struct Node{
int L,R,mid;
int Covered;
int Len;
Node *pLeft,*pRight;
Node(int l=0,int r=0,double len=0,int c=0,Node *pl=NULL,Node *pr=NULL)
:L(l),R(r),Len(len),Covered(c),pLeft(pl),pRight(pr){ mid=(L+R)/2;}
}tree[maxn*3];
struct Line{
int x,y1,y2;
bool bLeft;
Line(int x=0,int y1=0,int y2=0,bool bl=false):x(x),y1(y1),y2(y2),bLeft(bl){}
bool operator < (const Line& l) const {
return x<l.x;
}
}line[maxn*2];
void BuildTree(Node *root,int s,int e)
{
*root=Node(s,e);
if(s==e) return;
root->pLeft=++nNode+tree;
root->pRight=++nNode+tree;
BuildTree(root->pLeft,s,root->mid);
BuildTree(root->pRight,root->mid+1,e);
}
void Add(Node *root,int s,int e)
{
if(root->L==s&&root->R==e) {
root->Len=y[e+1]-y[s];
root->Covered++;
return;
}
if(e<=root->mid) Add(root->pLeft,s,e);
else if(s>=root->mid+1) Add(root->pRight,s,e);
else {
Add(root->pLeft,s,root->mid);
Add(root->pRight,root->mid+1,e);
}
if(root->Covered==0) root->Len=root->pLeft->Len+root->pRight->Len;
}
void Delete(Node *root,int s,int e)
{
if(root->L==s&&root->R==e){
root->Covered--;
if(root->Covered==0){
if(s==e) root->Len=0;
else root->Len=root->pLeft->Len+root->pRight->Len;
}
return;
}
if(e<=root->mid) Delete(root->pLeft,s,e);
else if(s>=root->mid+1) Delete(root->pRight,s,e);
else {
Delete(root->pLeft,s,root->mid);
Delete(root->pRight,root->mid+1,e);
}
if(root->Covered==0)
root->Len=root->pLeft->Len+root->pRight->Len;
}
int main()
{
int x1,x2,y1,y2;
while(scanf("%d%d%d%d",&x1,&y1,&x2,&y2)&&x1!=-1)
{
int nline=0,ycnt=0;
y[ycnt++]=y1; y[ycnt++]=y2;
line[nline++]=Line(x1,y1,y2,true);
line[nline++]=Line(x2,y1,y2,false);
while(scanf("%d%d%d%d",&x1,&y1,&x2,&y2)&&x1!=-1)
{
y[ycnt++]=y1; y[ycnt++]=y2;
line[nline++]=Line(x1,y1,y2,true);
line[nline++]=Line(x2,y1,y2,false);
}
sort(y,y+ycnt); sort(line,line+nline);
ycnt=unique(y,y+ycnt)-y;
nNode=0; BuildTree(tree,0,ycnt-2);
int area=0;
for(int i=0;i<nline-1;i++)
{
int L=find(y,y+ycnt,line[i].y1)-y;
int R=find(y,y+ycnt,line[i].y2)-y;
if(line[i].bLeft) Add(tree,L,R-1);
else Delete(tree,L,R-1);
area+=(line[i+1].x-line[i].x)*tree[0].Len;
}
cout<<area<<endl;
}
return 0;
}