POJ1151Atlantis 矩形面积并[线段树 离散化 扫描线]

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <map>
using namespace std;
const int N=205;
#define m (l+r)/2
#define lson o<<1,l,m
#define rson o<<1|1,m+1,r
#define lc o<<1
#define rc o<<1|1
inline int read(){
    char c=getchar();int x=0,f=1;
    while(c<‘0‘||c>‘9‘){if(c==‘-‘)f=-1;c=getchar();}
    while(c>=‘0‘&&c<=‘9‘){x=x*10+c-‘0‘;c=getchar();}
    return x*f;
}
int n,cnt=0;
double x1,y1,x2,y2,mp[N];
struct seg{
    double l,r,h;
    int f;//1 or -1
    seg(double a=0,double b=0,double c=0,int d=0):l(a),r(b),h(c),f(d){}
    bool operator <(const seg &r)const{return h<r.h;}
}a[N];
struct node{
    double sum;
    int cov;
}t[N<<2];
inline int Bin(double v){
    int l=1,r=cnt;
    while(l<=r){
        int mid=(l+r)>>1;
        if(mp[mid]==v) return mid;
        else if(v<mp[mid]) r=mid-1;
        else l=mid+1;
    }
    return -1;
}
inline void pushUp(int o,int l,int r){
    if(t[o].cov) t[o].sum=mp[r+1]-mp[l];
    else if(l==r) t[o].sum=0;
    else t[o].sum=t[lc].sum+t[rc].sum;
}
void update(int o,int l,int r,int ql,int qr,int v){
    if(ql<=l&&r<=qr){
        t[o].cov+=v;
        pushUp(o,l,r);
    }else{
        if(ql<=m) update(lson,ql,qr,v);
        if(m<qr) update(rson,ql,qr,v);
        pushUp(o,l,r);
    }
}
int cas=0;
int main(int argc, const char * argv[]) {
    while((n=read())){
        double ans=0;
        for(int i=1;i<=n;i++){
            scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2);
            a[i*2-1]=seg(x1,x2,y1,1);
            a[i*2]=seg(x1,x2,y2,-1);
            mp[2*i-1]=x1;
            mp[2*i]=x2;
        }
        sort(mp+1,mp+1+2*n);
        sort(a+1,a+1+2*n);
        cnt=0;mp[++cnt]=mp[1];
        for(int i=2;i<=2*n;i++)
            if(mp[i]!=mp[i-1]) mp[++cnt]=mp[i];
        memset(t,0,sizeof(t));
        for(int i=1;i<=2*n-1;i++){//最后一个不用
            int ql=Bin(a[i].l),qr=Bin(a[i].r)-1;
            if(ql<=qr) update(1,1,cnt,ql,qr,a[i].f);
            ans+=t[1].sum*(a[i+1].h-a[i].h);
        }
        printf("Test case #%d\n",++cas);
        printf("Total explored area: %.2f\n\n",ans);
    }
    
    return 0;
}