分析
就是把维护颜色段和树结合起来，
注意拼接的时候要减去中间相同的部分
代码
#include <cstdio>
#include <cctype>
#include <algorithm>
#define rr register
using namespace std;
const int N=100011; struct node{int y,next;}e[N<<1];
int dep[N],as[N],fat[N],top[N],dfn[N],tot,son[N],n,Lc,Rc,lL,rR,m;
int col[N],nfd[N],big[N],w[N<<2],lazy[N<<2],lc[N<<2],rc[N<<2],k=1;
inline signed iut(){
rr int ans=0; rr char c=getchar();
while (!isdigit(c)) c=getchar();
while (isdigit(c)) ans=(ans<<3)+(ans<<1)+(c^48),c=getchar();
return ans;
}
inline void print(int ans){
if (ans>9) print(ans/10);
putchar(ans%10+48);
}
inline void add(int x,int y){
e[++k]=(node){y,as[x]},as[x]=k,
e[++k]=(node){x,as[y]},as[y]=k;
}
inline void pup(int k){
lc[k]=lc[k<<1],rc[k]=rc[k<<1|1];
w[k]=w[k<<1]+w[k<<1|1]-(rc[k<<1]==lc[k<<1|1]);
}
inline void pdown(int k){
lc[k<<1]=lc[k<<1|1]=lc[k],lazy[k<<1]=lazy[k<<1|1]=1,
rc[k<<1]=rc[k<<1|1]=rc[k],w[k<<1]=w[k<<1|1]=1,lazy[k]=0;
}
inline void build(int k,int l,int r){
if (l==r){
lc[k]=rc[k]=col[nfd[l]],w[k]=1;
return;
}
rr int mid=(l+r)>>1;
build(k<<1,l,mid);
build(k<<1|1,mid+1,r);
pup(k);
}
inline void update(int k,int l,int r,int x,int y,int z){
if (l==x&&r==y){
lc[k]=rc[k]=z,w[k]=lazy[k]=1;
return;
}
if (lazy[k]) pdown(k);
rr int mid=(l+r)>>1;
if (y<=mid) update(k<<1,l,mid,x,y,z);
else if (x>mid) update(k<<1|1,mid+1,r,x,y,z);
else update(k<<1,l,mid,x,mid,z),
update(k<<1|1,mid+1,r,mid+1,y,z);
pup(k);
}
inline signed query(int k,int l,int r,int x,int y){
if (l==x&&r==y){
if (l==lL) Lc=lc[k];
if (r==rR) Rc=rc[k];
return w[k];
}
if (lazy[k]) pdown(k);
rr int mid=(l+r)>>1;
if (y<=mid) return query(k<<1,l,mid,x,y);
else if (x>mid) return query(k<<1|1,mid+1,r,x,y);
else {
rr int ansL=query(k<<1,l,mid,x,mid),
ansR=query(k<<1|1,mid+1,r,mid+1,y);
return ansL+ansR-(rc[k<<1]==lc[k<<1|1]);
}
}
inline void dfs1(int x,int fa){
dep[x]=dep[fa]+1,fat[x]=fa,son[x]=1;
for (rr int i=as[x],mson=-1;i;i=e[i].next)
if (e[i].y!=fa){
dfs1(e[i].y,x);
son[x]+=son[e[i].y];
if (son[e[i].y]>mson) big[x]=e[i].y,mson=son[e[i].y];
}
}
inline void dfs2(int x,int linp){
dfn[x]=++tot,nfd[tot]=x,top[x]=linp;
if (!big[x]) return; dfs2(big[x],linp);
for (rr int i=as[x];i;i=e[i].next)
if (e[i].y!=fat[x]&&e[i].y!=big[x]) dfs2(e[i].y,e[i].y);
}
inline void Update(int x,int y,int z){
for (;top[x]!=top[y];x=fat[top[x]]){
if (dep[top[x]]<dep[top[y]]) x^=y,y^=x,x^=y;
update(1,1,n,dfn[top[x]],dfn[x],z);
}
if (dep[x]>dep[y]) x^=y,y^=x,x^=y;
update(1,1,n,dfn[x],dfn[y],z);
}
inline signed Query(int x,int y){
int ans=0,xLc=-1,yLc=-1;
for (;top[x]!=top[y];x=fat[top[x]]){
if (dep[top[x]]<dep[top[y]]){
x^=y,y^=x,x^=y;
if (xLc^yLc) xLc^=yLc,yLc^=xLc,xLc^=yLc;
}
lL=dfn[top[x]],rR=dfn[x];
ans+=query(1,1,n,dfn[top[x]],dfn[x]);
ans-=(Rc==xLc),xLc=Lc;
}
if (dep[x]<dep[y]){
x^=y,y^=x,x^=y;
if (xLc^yLc) xLc^=yLc,yLc^=xLc,xLc^=yLc;
}
lL=dfn[y],rR=dfn[x];
ans+=query(1,1,n,dfn[y],dfn[x]);
ans-=(Rc==xLc)+(Lc==yLc);//除了x的拼接还有y的拼接
return ans;
}
signed main(){
n=iut(); m=iut();
for (rr int i=1;i<=n;++i) col[i]=iut();
for (rr int i=1;i<n;++i) add(iut(),iut());
dfs1(1,0),dfs2(1,1),build(1,1,n);
for (;m;--m){
rr char c=getchar();
while (c!='C'&&c!='Q') c=getchar();
rr int x=iut(),y=iut();
if (c=='C') Update(x,y,iut());
else print(Query(x,y)),putchar(10);
}
return 0;
}