POJ 1151 Atlantis 扫描线+线段树

Description

Input

Output

Sample Input

2
10 10 20 20
15 15 25 25.5
0

Sample Output

Test case #1
Total explored area: 180.00 

Source

//208K	16MS
#include<stdio.h>
#include<algorithm>
#define M 207
using namespace std;
double y[M];
struct Tree
{
    int l,r,mid,cover;
    double len;
}tree[M<<4];
struct Line
{
    double x,y1,y2;
    int dir;
}l[M<<4];
int cmp(Line a,Line b)
{
    return a.x<b.x;
}
void cal(int i)
{
    if(tree[i].cover>0)tree[i].len=y[tree[i].r]-y[tree[i].l];//如果被覆盖那么就是整段长度
    else if(tree[i].l+1==tree[i].r)tree[i].len=0;//未被覆盖且为叶子节点，则为0
    else tree[i].len=tree[i*2].len+tree[i*2+1].len;//非叶子节点即为下面子区间的覆盖总和
}
void build(int left,int right,int i)
{
    tree[i].l=left;tree[i].r=right;tree[i].mid=(left+right)>>1;
    tree[i].cover=0;tree[i].len=0;
    if(left+1!=right)
    {
        build(left,tree[i].mid,i*2);
        build(tree[i].mid,right,i*2+1);
    }
}
void insert(Line a,int i)
{
    Line t;
    if(y[tree[i].l]==a.y1&&y[tree[i].r]==a.y2)tree[i].cover+=a.dir;
    else
    {
        if(y[tree[i*2].r]>=a.y2)insert(a,i*2);
        else if(y[tree[i*2+1].l]<=a.y1)insert(a,i*2+1);
        else
        {
            t=a;
            t.y2=y[tree[i*2].r];
            insert(t,i*2);
            t=a;
            t.y1=y[tree[i*2+1].l];
            insert(t,i*2+1);
        }
    }
    cal(i);
}
int main()
{
    int n,cas=1;
    while(scanf("%d",&n),n)
    {
        double x1,y1,x2,y2,ans=0;
        int k=0;
        for(int i=1;i<=n;i++)
        {
            scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
            l[k].x=x1;l[k].y1=y1;l[k].y2=y2;l[k].dir=1;
            y[k++]=y1;
            l[k].x=x2;l[k].y1=y1;l[k].y2=y2;l[k].dir=-1;
            y[k++]=y2;
        }
        sort(l,l+k,cmp);
        sort(y,y+k);
        build(0,k-1,1);
        insert(l[0],1);
        for(int i=1;i<k;i++)
        {
            ans+=tree[1].len*(l[i].x-l[i-1].x);
            insert(l[i],1);
        }
        printf("Test case #%d\n",cas++);
        printf("Total explored area: %.2lf\n\n",ans);
    }
    return 0;
}