codevs3044

codevs3044

题面

大意：给出n个矩形求覆盖的总面积

看了hzwer的blog 似懂非懂 链接

可能还要多练点吧qaq

#include <bits/stdc++.h>
using namespace std;
#define N 10005
int n,m;
struct node{double x1,x2,y; int op;}line[N];
inline bool cmp(node a,node b){return a.y < b.y;}
double hash[N];
struct SegmentTree{int l,r,co; double sum;}Tree[N<<];
inline void pushup(int x)
{
    int l=Tree[x].l,r=Tree[x].r;
    if(Tree[x].co>)Tree[x].sum=hash[r+]-hash[l];
    else if(l==r) Tree[x].sum=;
    else Tree[x].sum=Tree[x<<].sum+Tree[x<<|].sum;
}
inline void build(int l,int r,int x)
{
    Tree[x].l=l; Tree[x].r=r; Tree[x].co=;
    if(l==r){Tree[x].sum=;return;}
    int mid=(l+r)>>; build(l,mid,x<<); build(mid+,r,x<<|); pushup(x);
}
inline void updata(int l,int r,int x,int val)
{
    if(l<=Tree[x].l&&Tree[x].r<=r){ Tree[x].co+=val; pushup(x); return;}
    int mid=(Tree[x].l+Tree[x].r)>>;
    if(l<=mid) updata(l,r,x<<,val); if(r>mid) updata(l,r,x<<|,val); pushup(x);
}
int main()
{
    while(~scanf("%d",&n))
    {
        int i; double x1,y1,x2,y2,ans=; if(n==) break;
        for(i=;i<=n;i++)
        {
            scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
            line[i*-].x1=line[i*].x1=x1;
            line[i*-].x2=line[i*].x2=x2;
            line[i*-].y=y1; line[i*-].op=-;
            line[i*].y=y2; line[i*].op=;
            hash[i*-]=x1; hash[i*]=x2;
        }
        n*=; sort(line+,line+n+,cmp); sort(hash+,hash+n+); m=unique(hash+,hash+n+)-hash-; build(,m,);
        for(i=n;i>=;i--)
        {
            int l=lower_bound(hash+,hash+m+,line[i].x1)-hash,r=lower_bound(hash+,hash+m+,line[i].x2)-hash-;
            updata(l,r,,line[i].op); ans+=(line[i].y-line[i-].y)*Tree[].sum;
        }
        printf("%.2lf\n",ans);
    }
}