【HDU】1542 Atlantis

#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<cmath>
#define EPS 1e-9
#define MAXN 210
struct Line
{
    double left,right,high;
    int flag;
};
struct node
{
    int cover;
    double len;
};
node tree[MAXN<<2];
Line p[MAXN];
double x[MAXN];
int cmp1(const void *a,const void *b)
{
    return (*(Line *)a).high>(*(Line *)b).high?1:-1;
}
int cmp2(const void *a,const void *b)
{
    return *(double *)a>*(double *)b?1:-1;
}
bool Equal(double x,double y)
{
    return fabs(x-y)<EPS;
}
void Build(int L,int R,int rt)
{
    tree[rt].cover=0;
    tree[rt].len=0;
    if(L!=R)
    {
        int mid=(L+R)>>1;
        Build(L,mid,rt<<1);
        Build(mid+1,R,rt<<1|1);
    }
}
int Bin(double val,int low,int high)
{
    int mid;
    while(low<high)
    {
        mid=(low+high)>>1;
        if(Equal(val,x[mid]))
            return mid;
        if(val>x[mid])
            low=mid+1;
        else
            high=mid;
    }
}
inline void PushUp(int L,int R,int rt)
{
    if(tree[rt].cover)
        tree[rt].len=x[R+1]-x[L];
    else if(L==R)
        tree[rt].len=0;
    else
        tree[rt].len=tree[rt<<1].len+tree[rt<<1|1].len;
}
void Update(int st,int en,int flag,int L,int R,int rt)
{
    if(st<=L&&R<=en)
    {
        tree[rt].cover+=flag;
        PushUp(L,R,rt);
    }
    else
    {
        int mid=(L+R)>>1;
        if(mid>=st)
            Update(st,en,flag,L,mid,rt<<1);
        if(en>mid)
            Update(st,en,flag,mid+1,R,rt<<1|1);
        PushUp(L,R,rt);
    }
}
int main()
{
    double x1,y1,x2,y2,ans;
    int n,m,i,k,u,v,ca=1;
    while(scanf("%d",&n),n)
    {
        for(i=k=0;i<n;i++)
        {
            scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
            x[k]=x1;
            p[k].flag=-1;
            p[k].left=x1;
            p[k].right=x2;
            p[k++].high=y2;
            x[k]=x2;
            p[k].flag=1;
            p[k].left=x1;
            p[k].right=x2;
            p[k++].high=y1;
        }
        qsort(p,k,sizeof(p[0]),cmp1);
        qsort(x,k,sizeof(x[0]),cmp2);
        for(m=i=0;i<k;i++)
        {
            if(!Equal(x[m],x[i]))
                x[++m]=x[i];
        }
        Build(0,m-1,1);
        for(ans=i=0;i<k-1;i++)
        {
            u=Bin(p[i].left,0,m+1);
            v=Bin(p[i].right,0,m+1);
            Update(u,v-1,p[i].flag,0,m-1,1);
            ans+=(p[i+1].high-p[i].high)*tree[1].len;
        }
        printf("Test case #%d\nTotal explored area: %.2lf\n\n",ca++,ans);
    }
    return 0;
}