SPOJ COT2 Count on a tree II [树上莫队]

#include <iostream>
#include <cstdio>
#include <algorithm>
#include <cstring>
#include <cmath>
using namespace std;
typedef long long ll;
const int N=2e5+5;
inline int read(){
char c=getchar();int x=0,f=1;
while(c<'0'||c>'9'){if(c=='-')f=-1;c=getchar();}
while(c>='0'&&c<='9'){x=x*10+c-'0';c=getchar();}
return x*f;
}

int n,Q,a
,mp
,u,v;
struct edge{int v,ne;} e[N<<1];
int cnt,h
;
inline void ins(int u,int v){
e[++cnt]=(edge){v,h[u]}; h[u]=cnt;
e[++cnt]=(edge){u,h[v]}; h[v]=cnt;
}
int block, pos
, m, st
, top;
int fa
[18], deep
, dfn
, dfc;
void dfs(int u){
dfn[u]=++dfc;
for(int i=1; (1<<i)<=deep[u]; i++)
fa[u][i]=fa[ fa[u][i-1] ][i-1];
int bot=top;
for(int i=h[u];i;i=e[i].ne) if(e[i].v!=fa[u][0]){
fa[e[i].v][0]=u; deep[e[i].v]=deep[u]+1;
dfs(e[i].v);
if(top-bot>=block){
m++;
while(top!=bot) pos[st[top--]]=m;
}
}
st[++top]=u;
}
inline int lca(int x,int y){
if(deep[x]<deep[y]) swap(x, y);
int bin=deep[x]-deep[y];
for(int i=0;i<17;i++) if((1<<i)&bin) x=fa[x][i];
if(x==y) return x;
for(int i=16;i>=0;i--)
if(fa[x][i]!=fa[y][i]) x=fa[x][i], y=fa[y][i];
return x==y ? x : fa[x][0];
}

struct meow{
int u, v, id;
bool operator <(const meow &a) const {return pos[u]==pos[a.u] ? dfn[v]<dfn[a.v] : pos[u]<pos[a.u];}
}q
;

int vis
, cou
, now, ans
;
inline void Xor(int u){
if(!vis[u]) now+= (++cou[a[u]])==1;
else now-= (--cou[a[u]])==0;
vis[u]^=1;
}
inline void move(int x,int y){ //printf("%d --> %d  %d\n",x,y,now);
if(deep[x]<deep[y]) swap(x, y);
while(deep[x]>deep[y]) Xor(x), x=fa[x][0];
while(x!=y) Xor(x), Xor(y), x=fa[x][0], y=fa[y][0];
}
void modui(){
u=1, v=1;
for(int i=1;i<=Q;i++){
if(u!=q[i].u) move(u, q[i].u), u=q[i].u;
if(v!=q[i].v) move(v, q[i].v), v=q[i].v;
int anc=lca(u, v);
ans[q[i].id]= now + (cou[a[anc]]==0);
}
}
int main(){
freopen("in","r",stdin);
n=read(); Q=read();
for(int i=1;i<=n;i++) a[i]=mp[i]=read();
sort(mp+1, mp+1+n); mp[0]=unique(mp+1, mp+1+n)-mp-1;
for(int i=1;i<=n;i++) a[i]=lower_bound(mp+1, mp+1+mp[0], a[i])-mp;
for(int i=1;i<n ;i++) ins(read(), read() );
block= sqrt(n);
dfs(1);
while(top) pos[st[top--]]=m;
for(int i=1;i<=Q;i++){
u=read(), v=read(); if(pos[u]>pos[v]) swap(u, v);
q[i]=(meow){u, v, i};
}
sort(q+1, q+1+Q);
modui();
for(int i=1;i<=Q;i++) printf("%d\n",ans[i]);
}