luogu P1856 [USACO5.5]矩形周长Picture 扫描线 + 线段树

Posted 2022-01-22 guangheli

Code:

#include<bits/stdc++.h>
#define maxn 200007 
#define inf 100005   
using namespace std;
void setIO(string s)

    string in=s+".in"; 
    freopen(in.c_str(),"r",stdin); 

struct Edge

    int l,r,h,flag; 
edges[maxn];   
int n; 
namespace tr

    #define ls lson[o]
    #define rs rson[o]
    #define mid ((l+r)>>1) 
    int tot; 
    int lson[maxn<<2],rson[maxn<<2],lflag[maxn<<2],rflag[maxn<<2],sumv[maxn<<2],numv[maxn<<2],len[maxn<<2]; 
    int newnode()  return ++tot;          
    void pushup(int o,int l,int r)
    
        if(sumv[o]) 
        
            numv[o]=1;                 
            len[o]=r-l+1; 
            lflag[o]=rflag[o]=1;         
           
        else 
        
            len[o]=len[ls]+len[rs]; 
            numv[o]=numv[ls]+numv[rs]; 
            if(rflag[ls]&&lflag[rs]) --numv[o]; 
            lflag[o]=lflag[ls]; 
            rflag[o]=rflag[rs];                    
        
    
    void add(int &o,int l,int r,int L,int R,int v)
    
        if(!o) o=newnode(); 
        if(l>=L&&r<=R)
        
            sumv[o]+=v; 
            pushup(o,l,r); 
            return; 
        
        if(L<=mid) add(ls,l,mid,L,R,v); 
        if(R>mid) add(rs,mid+1,r,L,R,v); 
        pushup(o,l,r);         
    
;     
bool cmp(Edge a,Edge b)

    if(a.h==b.h)  return a.flag > b.flag;
    else  return a.h < b.h; 

int main()

    //  setIO("input"); 
    scanf("%d",&n); 
    int a,b,c,d,i,ed=0,j,root=0,last=0,ans=0;  
    for(i=1;i<=n;++i)
    
        scanf("%d%d%d%d",&a,&b,&c,&d); 
        edges[++ed].l=a,edges[ed].r=c-1,edges[ed].h=b,edges[ed].flag=1;         // 加边
        edges[++ed].l=a,edges[ed].r=c-1,edges[ed].h=d,edges[ed].flag=-1;        // 删边   
    
    sort(edges+1,edges+1+ed,cmp); 
    for(i=1;i<=ed;++i)
    
        tr::add(root,-inf,inf,edges[i].l,edges[i].r,edges[i].flag);                                 
        ans+=abs(tr::len[root]-last);    
        last=tr::len[root]; 
        ans+=((tr::numv[root]<<1)*(edges[i+1].h-edges[i].h)); 
    
    printf("%d\n",ans); 
    return 0;