When I hadn't learned cdq yet, I wrote the code orzzz
ref of the tree cover tree on luogu.
#include <algorithm>
#include <iostream>
#include <cstdio>
using namespace std;
int n, m, uu, vv, dp[100005], c[100005];
struct Node{
int val, zxz, zdz, idx;
}nd[100005], tmp[100005];
bool cmpzxz(Node x, Node y){
return x.zxz<y.zxz;
}
bool cmpidx(Node x, Node y){
return x.idx<y.idx;
}
int lb(int x){
return x&-x;
}
void add(int x, int v){
for(; x<=100000; x+=lb(x))
c[x] = max(c[x], v);
}
int query(int x){
int re=0;
for(; x; x-=lb(x))
re = max(re, c[x]);
return re;
}
void clr(int x){
for(; x<=100000; x+=lb(x))
c[x] = 0;
}
void cdq(int l, int r){
if(l==r) return ;
int mid=(l+r)>>1;
cdq(l, mid);
sort(nd+mid+1, nd+r+1, cmpzxz);
int qaq=l;
for(int i=mid+1; i<=r; i++){
while(qaq<=mid && nd[qaq].val<=nd[i].zxz){
add(nd[qaq].zdz, dp[nd[qaq].idx]);
qaq++;
}
dp[nd[i].idx] = max(dp[nd[i].idx], query(nd[i].val)+1);
}
for(int i=l; i<qaq; i++) clr(nd[i].zdz);
sort(nd+mid+1, nd+r+1, cmpidx);
cdq(mid+1, r);
int jj=l, kk=mid+1;
for(int i=l; i<=r; i++)
if(jj<=mid && (kk>r || nd[jj].val<=nd[kk].val)) tmp[i] = nd[jj++];
else tmp[i] = nd[kk++];
for(int i=l; i<=r; i++)
nd[i] = tmp[i];
}
int main(){
cin>>n>>m;
for(int i=1; i<=n; i++){
scanf("%d", &nd[i].val);
nd[i].zdz = nd[i].zxz = nd[i].val;
nd[i].idx = i;
dp[i] = 1;
}
for(int i=1; i<=m; i++){
scanf("%d %d", &uu, &vv);
nd[uu].zdz = max(nd[uu].zdz, vv);
nd[uu].zxz = min(nd[uu].zxz, vv);
}
cdq(1, n);
int ans=0;
for(int i=1; i<=n; i++)
ans = max(ans, dp[i]);
cout<<ans<<endl;
return 0;
}