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 题意：中文题题意很明显。

分析：树链剖分+线段树（区间查询，单点查询，区间合并+区间合并），要注意的是，在Update时，如果更新的不是一个结点蕴含的区间，要注意两个区间相邻结点颜色是否相同，在Find时，也要看两条链相邻结点颜色是否相同，这里的相邻指的是从一个点只要走一条边就能到达另一个结点。

参考代码：

#include<cstdio>#include<cmath>#include<cstring>#include<algorithm>#include<iostream>using namespace std;#define mem(a,b) memset(a,b,sizeof(a))#define lson rt<<1#define rson rt<<1|1const int maxn = 1e5+10;int n,m;int col[maxn];//初始颜色int head[maxn],tot;struct Edge{    int to,next;}edge[maxn<<1];int siz[maxn],fa[maxn],son[maxn],dep[maxn];int p[maxn],fp[maxn],top[maxn],poi;//线段树,区间更新区间查询int sum[maxn<<2],lc[maxn<<2],rc[maxn<<2],tag[maxn<<2];//区间颜色和，左右颜色void Init(){    tot = poi = 0;    mem(head,-1);    mem(son,-1);}void AddEdge( int u, int v){    edge[tot].to = v;    edge[tot].next = head[u];    head[u] = tot++;}void dfs1( int u, int pre, int d){    siz[u] = 1;    fa[u] = pre;    dep[u] = d;    for( int i = head[u]; ~i; i = edge[i].next)    {        int v = edge[i].to;        if( v != pre)        {            dfs1(v,u,d+1);            siz[u] += siz[v];            if( son[u] == -1 || siz[v] > siz[son[u]])                son[u] = v;        }    }}void dfs2( int u, int tp){    top[u] = tp;    p[u] = ++poi;    fp[p[u]] = u;    if( son[u] == -1)        return;    dfs2(son[u],tp);    for( int i = head[u]; ~i; i = edge[i].next)    {        int v = edge[i].to;        if( v != fa[u] && v!= son[u])            dfs2(v,v);    }}void PushUp( int rt){    sum[rt] = sum[lson]+sum[rson]-(rc[lson]==lc[rson]);    lc[rt] = lc[lson];    rc[rt] = rc[rson];}void Build( int l, int r, int rt){    tag[rt] = 0;    if( l == r)    {        sum[rt] = 1;        lc[rt] = rc[rt] = col[fp[l]];        return;    }    int mid = (l+r)>>1;    Build(l,mid,lson);    Build(mid+1,r,rson);    PushUp(rt);}void PushDown( int rt){    if( tag[rt])    {        sum[lson] = sum[rson] = 1;        lc[lson] = lc[rson] = rc[lson] = rc[rson] = lc[rt];        tag[lson] = tag[rson] = tag[rt];        tag[rt] = 0;    }}void Update( int l, int r, int rt, int L, int R, int color){    if( L == l && R == r)    {        sum[rt] = 1;        lc[rt] = rc[rt] = color;        tag[rt] = 1;        return;    }    PushDown(rt);    int mid = (l+r)>>1;    if( R <= mid)        Update(l,mid,lson,L,R,color);    else if( L > mid)        Update(mid+1,r,rson,L,R,color);    else    {        Update(l,mid,lson,L,mid,color);        Update(mid+1,r,rson,mid+1,R,color);    }    PushUp(rt);}int Query( int l, int r, int rt, int L, int R){    if( L == l && R == r)        return sum[rt];    PushDown(rt);    int mid = (l+r)>>1;    if( R <= mid)        return Query(l,mid,lson,L,R);    else if( L > mid)        return Query(mid+1,r,rson,L,R);    else        return Query(l,mid,lson,L,mid)+Query(mid+1,r,rson,mid+1,R)-(rc[lson]==lc[rson]);}void Change( int u, int v, int color){    int t1 = top[u];    int t2 = top[v];    while( t1 != t2)    {        if( dep[t1] < dep[t2])        {            swap(u,v);            swap(t1,t2);        }        Update(1,poi,1,p[t1],p[u],color);        u = fa[t1];        t1 = top[u];    }    if( dep[u] > dep[v])        swap(u,v);    Update(1,poi,1,p[u],p[v],color);}int Check( int l, int r, int rt, int pos){    if( l == pos && r == pos)        return lc[rt];    PushDown(rt);    int mid = (l+r)>>1;    if( pos <= mid)        return Check(l,mid,lson,pos);    else        return Check(mid+1,r,rson,pos);}int Find( int u, int v){    int ans = 0;    int t1 = top[u];    int t2 = top[v];    while( t1 != t2)    {        if( dep[t1] < dep[t2])        {            swap(u,v);            swap(t1,t2);        }        ans += Query(1,poi,1,p[t1],p[u]);        if( Check(1,poi,1,p[t1]) == Check(1,poi,1,p[fa[t1]]))            ans--;        u = fa[t1];        t1 = top[u];    }    if( dep[u] > dep[v])        swap(u,v);    ans += Query(1,poi,1,p[u],p[v]);    return ans;}int main(){    while( ~scanf("%d%d",&n,&m))    {        Init();        for( int i = 1; i <= n; i++)            scanf("%d",&col[i]);        int u,v;        for( int i = 1; i < n; i++)        {            scanf("%d%d",&u,&v);            AddEdge(u,v);            AddEdge(v,u);        }        dfs1(1,0,0);        dfs2(1,1);        Build(1,poi,1);        while( m--)        {            char op[3];            int a,b,color;            scanf("%s",op);            if( op[0] == 'C')            {                scanf("%d%d%d",&a,&b,&color);                Change(a,b,color);            }            else if( op[0] == 'Q')            {                scanf("%d%d",&a,&b);                printf("%d\n",Find(a,b));            }        }    }    return 0;}