线段树专辑—— hdu 1255 覆盖的面积

#include<iostream>
#include<string>
#include<stdlib.h>
using namespace std;

typedef struct
{
double x;
double y_up;
double y_down;
int l_r;
}LINE;

typedef struct
{
double x;
double y_up;
double y_down;
int cover;
bool has_child;
}TREE;

int cmp(const void *a,const void *b)
{
return *(double *)a>*(double *)b? 1: -1;
}

TREE tree[1000*1001];
LINE line[2002];
int n,index;
double x1,y1,x2,y2;
double y[2002];

void build(int i,int l,int r)
{
tree[i].cover=0;
tree[i].x=-1;
tree[i].has_child=true;
tree[i].y_up=y[r];
tree[i].y_down=y[l];
if(l+1==r)
{
tree[i].has_child=false;
return;
}
int mid=(l+r)>>1;
build(2*i,l,mid);
build(2*i+1,mid,r);
}

double insert(int i,double l,double r,double x,int l_r)
{
if(tree[i].y_up<=l || tree[i].y_down>=r)
return 0;
if(!tree[i].has_child)
{
if(tree[i].cover>1)
{
double ans=(x-tree[i].x)*(tree[i].y_up-tree[i].y_down);
tree[i].x=x;
tree[i].cover+=l_r;
return ans;
}
else
{
tree[i].cover+=l_r;
tree[i].x=x;
return 0;
}
}
else
return insert(2*i,l,r,x,l_r)+insert(2*i+1,l,r,x,l_r);
}

int main()
{
int t,i;
//freopen("D:\\in.txt","r",stdin);
cin>>t;
while(t--)
{
cin>>n;
index=1;
for(i=1;i<=n;i++)
{
scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
line[index].x=x1;
line[index].l_r=1;
line[index].y_up=y2;
line[index].y_down=y1;
y[index]=y1;
index++;

line[index].x=x2;
line[index].l_r=-1;
line[index].y_up=y2;
line[index].y_down=y1;
y[index]=y2;
index++;
}
qsort(y+1,2*n,sizeof(y[0]),cmp);
qsort(line+1,2*n,sizeof(line[0]),cmp);
build(1,1,index-1);
double ans=0;
for(i=1;i<index;i++)
{
ans+=insert(1,line[i].y_down,line[i].y_up,line[i].x,line[i].l_r);
}
printf("%.2lf\n",ans);
}
return 0;
}