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| #include<bits/stdc++.h>
using namespace std;
typedef long long LL;
inline int Get_Int() {
int num=0,bj=1;
char x=getchar();
while(!isdigit(x)) {if(x=='-')bj=-1;x=getchar();}
while(isdigit(x)) {num=num*10+x-'0';x=getchar();}
return num*bj;
}
const int maxn=100005,K=2;
int D;
struct Point {
int d[K],Min[K],Max[K],id;
int ls,rs,val;
int& operator [] (int x) {return d[x];}
bool operator < (const Point& b) const {return d[D]<b.d[D];}
} p[maxn];
int ans,ansid;
struct KD_Tree {
#define lson p[index].ls
#define rson p[index].rs
void update(int index) {
for(int i=0; i<K; i++) {
p[index].Max[i]=p[index].Min[i]=p[index][i];
if(lson) {
p[index].Min[i]=min(p[index].Min[i],p[lson].Min[i]);
p[index].Max[i]=max(p[index].Max[i],p[lson].Max[i]);
}
if(rson) {
p[index].Min[i]=min(p[index].Min[i],p[rson].Min[i]);
p[index].Max[i]=max(p[index].Max[i],p[rson].Max[i]);
}
}
}
int build(int Left,int Right,int now) {
int mid=(Left+Right)>>1,root=mid;
D=now;
nth_element(p+Left,p+mid,p+Right+1);
if(Left<mid)p[root].ls=build(Left,mid-1,(now+1)%K);
if(Right>mid)p[root].rs=build(mid+1,Right,(now+1)%K);
update(root);
return root;
}
LL dist(Point a,Point b) {
LL ans=0;
for(int i=0; i<K; i++)ans+=abs(a[i]-b[i]);
return ans;
}
int get_min(int index,Point P) {
if(!index)return INT_MAX/2;
int ans=0;
for(int i=0; i<K; i++) {
if(p[index].Min[i]-P[i]>0)ans+=abs(p[index].Min[i]-P[i]);
if(P[i]-p[index].Max[i]>0)ans+=abs(P[i]-p[index].Max[i]);
}
return ans;
}
void find_min(int index,Point P,int now) {
if(!index)return;
if(p[index].id!=P.id) {
LL Dist=dist(p[index],P);
if(Dist<ans||(Dist==ans&&p[index].id<ansid))ans=Dist,ansid=p[index].id;
}
LL ldist=get_min(lson,P),rdist=get_min(rson,P);
if(ldist<=rdist) {
if(ldist<=ans)find_min(lson,P,(now+1)%K);
if(rdist<=ans&&P[now]+ans>=p[index][now])find_min(rson,P,(now+1)%K);
} else {
if(rdist<=ans)find_min(rson,P,(now+1)%K);
if(ldist<=ans&&P[now]-ans<=p[index][now])find_min(lson,P,(now+1)%K);
}
}
} kdtree;
int n,f[maxn],g[maxn],First=0,Second=0,Max=0,maxlen=0;
bool vst[maxn];
vector<int> edges[maxn];
void Dfs(int Now) {
vst[Now]=1;
for(int Next:edges[Now]) {
if(vst[Next])continue;
Dfs(Next);
if(f[Next]+1>f[Now]) {
g[Now]=f[Now];
f[Now]=f[Next]+1;
} else g[Now]=max(g[Now],f[Next]+1);
maxlen=max(maxlen,f[Now]+g[Now]);
}
}
int main() {
n=Get_Int();
for(int i=1; i<=n; i++) {
p[i][0]=Get_Int();
p[i][1]=Get_Int();
p[i].id=i;
}
int root=kdtree.build(1,n,0);
for(int i=1; i<=n; i++) {
ans=ansid=INT_MAX;
kdtree.find_min(root,p[i],0);
edges[p[i].id].push_back(ansid);
edges[ansid].push_back(p[i].id);
}
for(int i=1; i<=n; i++) {
if(vst[i])continue;
maxlen=0;
Dfs(i);
if((maxlen+1)/2>First) {
Second=First;
First=(maxlen+1)/2;
} else Second=max(Second,(maxlen+1)/2);
Max=max(Max,maxlen);
}
printf("%d\n",max(Max,First+Second+2));
return 0;
}
|
