HDU 1828 Picture(线段树:扫描线 面积并)

题解+扫描线讲解：https://blog.csdn.net/u013480600/article/details/22548393

#include<bits/stdc++.h>
#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cmath>
#include<cstring>
#include<queue>
#include<set>
#include<map>
#include<vector>

#define inf 0x3f3f3f3f
#define mem(a,b) memset(a,b,sizeof(a))
#define ll long long
#define sd(x) scanf("%d",&(x))
#define sl(x) scanf("%lld",&(x))
#define slf(x) scanf("%lf",&(x))
#define scs(s) scanf("%s",s)
#define rep(i,a,b) for(int i=a;i<=b;i++)
#define per(i,a,b) for(int i=a;i>=b;i--)
#define lowbit(x) x&(-x)
#define ls now<<1
#define rs now<<1|1
#define lson l,mid,ls
#define rson mid+1,r,rs
#define All L,R

using namespace std;

const int maxn=2222;

struct node{
    double l,r,h;
    int d;
    bool operator <(const node cmp) const{
        return h<cmp.h;
    }
}e[maxn];

double Hash[maxn],tree[maxn*4];
int lazy[maxn*4];

void built(int l,int r,int now)
{
    int mid=(l+r)>>1;
    lazy[now]=tree[now]=0;
    if(l==r)
        return ;
    built(lson);
    built(rson);
}

void pushdown(int now,int l,int r)
{
    int mid=(l+r)>>1;
    if(lazy[now]!=-1)
    {
        lazy[ls]=lazy[rs]=lazy[now];
        tree[ls]=lazy[ls]?Hash[mid+1]-Hash[l]:0;
        tree[rs]=lazy[rs]?Hash[r+1]-Hash[mid+1]:0;
    }

}

void pushup(int now,int l,int r)
{
    if(lazy[ls]==-1||lazy[rs]==-1||(lazy[rs]!=lazy[ls]))
        lazy[now]=-1;
    else
        lazy[now]=lazy[ls];
    tree[now]=tree[ls]+tree[rs];
}

void update(int l,int r,int now,int L,int R,int c)
{
    int mid=(l+r)>>1;
    if(L<=l&&r<=R)
    {
        if(lazy[now]!=-1)
        {
            lazy[now]+=c;
            tree[now]=lazy[now]?Hash[r+1]-Hash[l]:0;
            return ;
        }
    }
    pushdown(now,l,r);
    if(L<=mid) update(lson,All,c);
    if(R>mid) update(rson,All,c);
    pushup(now,l,r);
}

int bin(double key,int n,double d[])
{
    int l=1,r=n;
    while(r>=l)
    {
        int m=(r+l)/2;
        if(d[m]==key)
            return m;
        else if(d[m]>key)
            r=m-1;
        else
            l=m+1;
    }
}

int main(){
    int t,tot=0;
    while(sd(t)&&t)
    {
        int n=0,m=0;
        double x1,x2,y1,y2;
        rep(i,1,t)
        {
            slf(x1),slf(y1),slf(x2),slf(y2);
            Hash[++n]=x1;
            Hash[++n]=x2;

            e[++m]=(node){x1,x2,y1,1};
            e[++m]=(node){x1,x2,y2,-1};
        }
        sort(e+1,e+1+m);
        sort(Hash+1,Hash+1+n);
        n=unique(Hash+1,Hash+1+n)-Hash-1;
        built(1,n-1,1);
        double ans=0;
        rep(i,1,m-1)
        {
            int l=lower_bound(Hash+1,Hash+1+n,e[i].l)-Hash;
            int r=lower_bound(Hash+1,Hash+1+n,e[i].r)-Hash-1;
            if(l<=r) update(1,n-1,1,l,r,e[i].d);
            ans+=tree[1]*(e[i+1].h-e[i].h);
        }
        printf("Test case #%d\nTotal explored area: %.2lf\n\n",++tot,ans);
    }
    return 0;
}