hdu 1255 矩形面积覆盖次数

#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>
using std::sort;
using std::unique;

const int size=1111;

struct Line
{
double lx,rx,y;
int f;
Line(){}
Line(double a,double b,double c,int d): lx(a),rx(b),y(c),f(d){}
bool operator < (const Line &cmp) const{
return y<cmp.y;
}
}line[size<<1];

double cov[size<<3],len1[size<<3],len2[size<<3];
double X[size<<1];

void PushUp(int rt,int l,int r)
{
if (cov[rt]>=2)
{
len2[rt]=X[r+1]-X[l];
len1[rt]=0;
}
else if (cov[rt])
{
if (l==r)
{
len1[rt]=X[r+1]-X[l];
len2[rt]=0;
}
else
{
len2[rt]=len1[rt<<1]+len1[rt<<1|1]+len2[rt<<1]+len2[rt<<1|1];
len1[rt]=X[r+1]-X[l]-len2[rt];
}
}
else if (l==r) len1[rt]=len2[rt]=0;
else
{
len2[rt]=len2[rt<<1]+len2[rt<<1|1];
len1[rt]=len1[rt<<1]+len1[rt<<1|1];
}
}

void update(int rt,int l,int r,int L,int R,int v)
{
if (L<=l&&r<=R)
{
cov[rt]+=v;
PushUp(rt,l,r);
return ;
}
int m=(l+r)>>1;
if (L<=m) update(rt<<1,l,m,L,R,v);
if (R>m)  update(rt<<1|1,m+1,r,L,R,v);
PushUp(rt,l,r);
}

int Fin(double key,int k)
{
int l=0,r=k;
while (l<=r)
{
int m=(l+r)>>1;
if (X[m]==key) return m;
else if (X[m]<key) l=m+1;
else r=m-1;
}
return -1;
}

int main()
{
int T,n,i,k,m,l,r;
double x1,x2,y1,y2,ans;
scanf("%d",&T);
while (T--)
{
scanf("%d",&n);
for (m=i=0;i<n;i++)
{
scanf("%lf %lf %lf %lf",&x1,&y1,&x2,&y2);
X[m]=x1; X[m+1]=x2;
line[m++]=Line(x1,x2,y1,1);
line[m++]=Line(x1,x2,y2,-1);
}
sort(X,X+m);
sort(line,line+m);
k=unique(X,X+m)-X-1;
memset(cov,0,sizeof(cov));
memset(len1,0,sizeof(len1));
memset(len2,0,sizeof(len2));
for (ans=i=0;i<m-1;i++)
{
l=Fin(line[i].lx,k);
r=Fin(line[i].rx,k)-1;
if (l<=r) update(1,0,k,l,r,line[i].f);
ans+=len2[1]*(line[i+1].y-line[i].y);
}
printf("%.2lf\n",ans);
}
return 0;
}