Ideas: Review interval, number of intervals to maintain the color of the line segment to segment, the left end point of the color range, the right end of the color range.
When the query, because the query path is divided into several sections, we have to maintain about the endpoint color.
For example: query UV: U and V are likely to jump, color pos1 must be recorded after each jump endpoint, pos2. For example, the query:
Query ux. The chain split tree, then the new number of x> new number u.
All inquiries from the segment tree x-> u. Query number of colors, and the maintenance of Lc and Rc is about this section endpoint color, and determines whether Rc pos1 same color and, if the same color value -1.
Pos = Lc and color.
If we jump v pos1 exchange and pos2. Pos1 and then each is compared.
If the last jump. We should pay attention:
To compare Lc and pos1, Rc and pos2.
Internal segment tree sympathy range queries should pay attention to compare the endpoint color.
//#include <bits/stdc++.h>
//#define Rint register int
//using namespace std;
//
//int main(){
//
// srand(time(0));
// int n=rand()%5+5, m=rand()%7+1;
// printf("%d %d\n", n, m);
// for(int i=1; i<=n; i++){
// cout<<rand()%4+1<<" ";
// }
// cout<<endl;
// for(int i=2; i<=n; i++){
// cout<<i<<" "<<rand()%(i-1)+1<<endl;
// }
// for(int i=1; i<=m; i++){
// int k, a, b, c;
// k=rand()%2;
// if(k){
// a=rand()%(n)+1;
// b=rand()%(n)+1;
// c=rand()%3+1;
// cout<<"C "<<a<<" "<<b<<" "<<c<<endl;
// }
// else{
// a=rand()%(n)+1;
// b=rand()%(n)+1;
// cout<<"Q "<<a<<" "<<b<<endl;
// }
// }
//
// return 0;
//}
#include <bits/stdc++.h>
#define Rint register int
using namespace std;
#define mid ((l+r)>>1)
#define lson rt<<1,l,mid
#define rson rt<<1|1,mid+1,r
#define len (r-l+1)
const int maxn=1000005;
int n,m;
//见题意
int tot,head[maxn],nex[maxn],to[maxn], w[maxn], wt[maxn];
//链式前向星数组，w[]、wt[]初始点权数组
int lc[maxn<<2], rc[maxn<<2], sc[maxn<<2], laz[maxn<<2];
//线段树数组 左端颜色 右端颜色 区间标记
int son[maxn],id[maxn],fa[maxn],cnt,dep[maxn],siz[maxn],top[maxn];
//son[]重儿子编号,id[]新编号,fa[]父亲节点,cnt dfs_clock/dfs序,dep[]深度,siz[]子树大小,top[]当前链顶端节点
int pos1, pos2, Lc, Rc,res;
//链左端颜色 链右端颜色 查询答案
inline void add(int x,int y){//链式前向星加边
to[++tot]=y;
nex[tot]=head[x];
head[x]=tot;
}
//-------------------------------------- 以下为线段树
inline void build(int rt,int l,int r){
if(l==r){
lc[rt]=rc[rt]=wt[l];
sc[rt]=1;
laz[rt]=0;
return;
}
build(lson);
build(rson);
sc[rt]=sc[rt<<1]+sc[rt<<1|1];
if(rc[rt<<1]==lc[rt<<1|1]){
sc[rt]--;
}
lc[rt]=lc[rt<<1];
rc[rt]=rc[rt<<1|1];
}
void down(int rt){
if(laz[rt]){
laz[rt<<1]=laz[rt<<1|1]=laz[rt];
sc[rt<<1]=sc[rt<<1|1]=sc[rt];
lc[rt<<1]=lc[rt<<1|1]=rc[rt<<1]=rc[rt<<1|1]=laz[rt];
laz[rt]=0;
}
}
inline void update(int rt, int l, int r, int L, int R, int k){
if(L<=l&&r<=R){
laz[rt]=lc[rt]=rc[rt]=k;
sc[rt]=1;
//cout<<"L "<<l<<" "<<r<<" "<<lc[rt]<<" "<<rc[rt]<<" "<<sc[rt]<<endl;
return;
}
else{
down(rt);
if(L<=mid)update(lson,L,R,k);
if(R>mid)update(rson,L,R,k);
sc[rt]=sc[rt<<1]+sc[rt<<1|1];
if(rc[rt<<1]==lc[rt<<1|1]){
sc[rt]--;
}
lc[rt]=lc[rt<<1];
rc[rt]=rc[rt<<1|1];
//cout<<"L "<<l<<" "<<r<<" "<<lc[rt]<<" "<<rc[rt]<<" "<<sc[rt]<<endl;
}
}
inline void query(int rt,int l,int r,int L,int R){
if(L<=l&&r<=R){
res+=sc[rt];
if(lc[rt]==Rc){
res--;
}
if(L==l){
Lc=lc[rt];
}
Rc=rc[rt];
return;
}
else{
if(laz[rt])down(rt);
if(L<=mid)query(lson,L,R);
if(R>mid)query(rson,L,R);
}
}
/*
7 100
1 1 1 1 1 1 1
1 2
2 3
3 5
3 4
2 6
1 7
C 1 2 2
Q 7 3
*/
//-------------------------------------- 以上为线段树
inline int Q(int x, int y){
pos1=pos2=0;res=0;
while(top[x]!=top[y]){//当两个点不在同一条链上
if(dep[top[x]]<dep[top[y]])swap(x,y), swap(pos1,pos2);//把x点改为所在链顶端的深度更深的那个点
Lc=Rc=0;
query(1,1,n,id[top[x]],id[x]);//ans加上x点到x所在链顶端 这一段区间的点权和
x=fa[top[x]];//把x跳到x所在链顶端的那个点的上面一个点
if(Rc==pos1){
res--;
}
pos1=Lc;
}
//直到两个点处于一条链上
Lc=Rc=0;
if(dep[x]>dep[y])swap(x,y), swap(pos1,pos2);//把x点深度更深的那个点
query(1,1,n,id[x],id[y]);//这时再加上此时两个点的区间和即可
if(Lc==pos1){
res--;
}
if(Rc==pos2){
res--;
}
return res;
}
inline void U(int x, int y, int k){
while(top[x]!=top[y]){
if(dep[top[x]]<dep[top[y]])swap(x,y);
update(1,1,n,id[top[x]],id[x],k);
x=fa[top[x]];
}
if(dep[x]>dep[y])swap(x,y);
update(1,1,n,id[x],id[y],k);
}
//-------------------------------------- 以下为模板
inline void dfs1(int x,int f,int deep){
dep[x]=deep;
fa[x]=f;
siz[x]=1;
int maxson=-1;
for(Rint i=head[x];i;i=nex[i]){
int y=to[i];
if(y==f)continue;
dfs1(y,x,deep+1);
siz[x]+=siz[y];
if(siz[y]>maxson)son[x]=y,maxson=siz[y];
}
}
inline void dfs2(int x,int topf){
id[x]=++cnt;
top[x]=topf;
//cout<<x<<" ; "<<cnt<<endl;
wt[cnt]=w[x];//把每个点的初始值赋到新编号上来
if(!son[x])return;
dfs2(son[x],topf);
for(Rint i=head[x];i;i=nex[i]){
int y=to[i];
if(y==fa[x]||y==son[x])continue;
dfs2(y,y);
}
}
int main(){
scanf("%d%d", &n, &m);
for(int i=1; i<=n; i++){
scanf("%d", &w[i]);
}
for(Rint i=1;i<n;i++){
int a,b;
scanf("%d%d", &a, &b);
add(a,b);add(b,a);
}
dfs1(1,0,1);
dfs2(1,1);
build(1,1,n);
while(m--){
char s[5];
int a, b, c;
scanf("%s", s);
if(s[0]=='C'){
scanf("%d%d%d", &a, &b, &c);
U(a, b, c);
}
else{
int a, b;
scanf("%d%d", &a, &b);
printf("%d\n", Q(a, b));
}
}
}
/*
6 6
4 2 2 4 3 1
2 1
3 1
4 2
5 3
6 3
C 6 2 1
C 1 2 3
Q 4 3
*/
