维护区间左颜色值，右颜色值，颜色段个数。
#include <iostream>
#include <cstdio>
using namespace std;
int n, m, uu, vv, ww, w[100005], wt[100005], qwq, idx[100005], hea[100005];
int cnt, dep[100005], siz[100005], son[100005], fa[100005], top[100005];
char ss[15];
struct Edge{
int too, nxt;
}edge[200005];
struct SGT{
int col[400005], lco[400005], rco[400005], tag[400005];
void upd(int o, int lson, int rson){
col[o] = col[lson] + col[rson];
if(rco[lson]==lco[rson]) col[o]--;
lco[o] = lco[lson];
rco[o] = rco[rson];
}
void build(int o, int l, int r){
if(l==r) lco[o] = rco[o] = wt[l], col[o] = 1;
else{
int mid=(l+r)>>1;
int lson=o<<1;
int rson=lson|1;
if(l<=mid) build(lson, l, mid);
if(mid<r) build(rson, mid+1, r);
upd(o, lson, rson);
}
}
void pushDown(int o, int l, int r, int lson, int rson, int mid){
col[lson] = col[rson] = 1;
lco[lson] = rco[lson] = lco[rson] = rco[rson] = tag[o];
tag[lson] = tag[rson] = tag[o];
tag[o] = 0;
}
void update(int o, int l, int r, int x, int y, int k){
if(l>=x && r<=y){
col[o] = 1;
lco[o] = rco[o] = tag[o] = k;
}
else{
int mid=(l+r)>>1;
int lson=o<<1;
int rson=lson|1;
if(tag[o]) pushDown(o, l, r, lson, rson, mid);
if(x<=mid) update(lson, l, mid, x, y, k);
if(mid<y) update(rson, mid+1, r, x, y, k);
upd(o, lson, rson);
}
}
int query(int o, int l, int r, int x, int y){
if(l>=x && r<=y) return col[o];
else{
int mid=(l+r)>>1;
int lson=o<<1;
int rson=lson|1;
int ans=0;
if(tag[o]) pushDown(o, l, r, lson, rson, mid);
if(x<=mid) ans += query(lson, l, mid, x, y);
if(mid<y) ans += query(rson, mid+1, r, x, y);
if(x<=mid && mid<y && rco[lson]==lco[rson]) return ans-1;
return ans;
}
}
int queryCol(int o, int l, int r, int x){
if(l==r) return lco[o];
else{
int mid=(l+r)>>1;
int lson=o<<1;
int rson=lson|1;
if(tag[o]) pushDown(o, l, r, lson, rson, mid);
if(x<=mid) return queryCol(lson, l, mid, x);
else return queryCol(rson, mid+1, r, x);
}
}
}sgt;
void add_edge(int fro, int too){
edge[++cnt].nxt = hea[fro];
edge[cnt].too = too;
hea[fro] = cnt;
}
void dfs1(int x, int f){
dep[x] = dep[f] + 1;
siz[x] = 1;
fa[x] = f;
int maxSon=-1;
for(int i=hea[x]; i; i=edge[i].nxt){
int t=edge[i].too;
if(t!=f){
dfs1(t, x);
siz[x] += siz[t];
if(maxSon<siz[t]) maxSon = siz[t], son[x] = t;
}
}
}
void dfs2(int x, int topf){
top[x] = topf;
idx[x] = ++qwq;
wt[qwq] = w[x];
if(!son[x]) return ;
dfs2(son[x], topf);
for(int i=hea[x]; i; i=edge[i].nxt){
int t=edge[i].too;
if(t!=fa[x] && t!=son[x])
dfs2(t, t);
}
}
void changeRange(int uu, int vv, int ww){
while(top[uu]!=top[vv]){
if(dep[top[uu]]<dep[top[vv]]) swap(uu, vv);
sgt.update(1, 1, n, idx[top[uu]], idx[uu], ww);
uu = fa[top[uu]];
}
if(dep[uu]>dep[vv]) swap(uu, vv);
sgt.update(1, 1, n, idx[uu], idx[vv], ww);
}
int queryRange(int uu, int vv){
int ans=0, orz, sto;
while(top[uu]!=top[vv]){
if(dep[top[uu]]<dep[top[vv]]) swap(uu, vv);
ans += sgt.query(1, 1, n, idx[top[uu]], idx[uu]);
orz = sgt.queryCol(1, 1, n, idx[top[uu]]);
sto = sgt.queryCol(1, 1, n, idx[fa[top[uu]]]);
if(orz==sto) ans--;
uu = fa[top[uu]];
}
if(dep[uu]>dep[vv]) swap(uu, vv);
ans += sgt.query(1, 1, n, idx[uu], idx[vv]);
return ans;
}
int main(){
cin>>n>>m;
for(int i=1; i<=n; i++) scanf("%d", &w[i]);
for(int i=1; i<n; i++){
scanf("%d %d", &uu, &vv);
add_edge(uu, vv);
add_edge(vv, uu);
}
dfs1(1, 0);
dfs2(1, 1);
sgt.build(1, 1, n);
while(m--){
scanf("%s", ss);
if(ss[0]=='C'){
scanf("%d %d %d", &uu, &vv, &ww);
changeRange(uu, vv, ww);
}
else{
scanf("%d %d", &uu, &vv);
printf("%d
", queryRange(uu, vv));
}
}
return 0;
}