扫描线矩形周长的并 POJ1177

 //扫描线矩形周长的并 POJ1177
 // 我是按x轴

 #include <iostream>
 #include <cstdio>
 #include <cstdlib>
 #include <algorithm>
 #include <vector>
 #include <cmath>
 #include <cstring>
 // #include <memory.h>
 // #include <bits/stdc++.h>
 using namespace std;
 #define LL long long
 typedef pair<int,int> pii;
 const LL inf = 0x3f3f3f3f;
 const LL MOD =100000000LL;
 const int N = ;
 const double eps = 1e-;
 void fre() {freopen("in.txt","r",stdin);}
 void freout() {freopen("out.txt","w",stdout);}
 inline int read() {int x=,f=;char ch=getchar();while(ch>''||ch<'') {if(ch=='-') f=-; ch=getchar();}while(ch>=''&&ch<='') {x=x*+ch-'';ch=getchar();}return x*f;}

 struct node{
     int x1,x2,y;
     int flag;
     bool operator < (const node &a) const{
         return y<a.y||(y==a.y&&flag>a.flag);
     }
 }e[N<<];

 int color[N<<];
 int sum[N<<],hashh[N<<];
 int cnt[N<<],pl[N<<],pr[N<<];
 void pushup(int rt,int l,int r){
     if(color[rt]) {
         sum[rt]=hashh[r+]-hashh[l];
         cnt[rt]=;
         pl[rt]=pr[rt]=;
     }
     else if(l!=r) {
         sum[rt]=sum[rt<<]+sum[rt<<|];
         cnt[rt]=cnt[rt<<]+cnt[rt<<|]-(pr[rt<<]&&pl[rt<<|]);
         pr[rt]=pr[rt<<|];
         pl[rt]=pl[rt<<];
     }
     else sum[rt]=cnt[rt]=pl[rt]=pr[rt]=;
 }
 void update(int l,int r,int L,int R,int rt,int f){
     if(l<=L&&R<=r){
         color[rt]+=f;
         pushup(rt,L,R);
         return;
     }
     int mid=(L+R)>>;
     if(l<=mid) update(l,r,L,mid,rt<<,f);
     if(r>mid) update(l,r,mid+,R,rt<<|,f);
     pushup(rt,L,R);
 }

 int main(){
     // fre();
     int n;
     scanf("%d",&n);
         memset(color,,sizeof(color));
         memset(sum,,sizeof(sum));
         memset(cnt,,sizeof(cnt));
         memset(pr,,sizeof(pr));
         memset(pl,,sizeof(pl));
         int x1,x2,y1,y2;
         for(int i=;i<=n;i++){
            scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
            e[i*-].x1=e[i*].x1=x1;
            e[i*-].x2=e[i*].x2=x2;
            e[i*-].y=y1,e[i*].y=y2;
            e[i*-].flag=,e[i*].flag=-;
            hashh[i*-]=x1,hashh[i*]=x2;
         }
         sort(e+,e++*n);
         sort(hashh+,hashh++*n);
         int ans=;
         int lastsum=;
         e[].y=e[].y;
         for(int i=;i<=*n;i++){
             ans+=(e[i].y-e[i-].y)**cnt[];
             int l=lower_bound(hashh+,hashh++*n,e[i].x1)-hashh;
             int r=lower_bound(hashh+,hashh++*n,e[i].x2)-hashh-;
             if(l<=r) update(l,r,,*n,,e[i].flag);
             ans+=abs(sum[]-lastsum);
             lastsum=sum[];
         }
         printf("%d\n",ans);
     return ;
 }