HYSBZ 2243（染色）

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <cstring>
#include <stack>
#include <cctype>
#include <queue>
#include <string>
#include <vector>
#include <set>
#include <map>
#include <climits>
#define lson rt<<1,l,mid
#define rson rt<<1|1,mid+1,r
#define fi first
#define se second
#define ping(x,y) ((x-y)*(x-y))
#define mst(x,y) memset(x,y,sizeof(x))
#define mcp(x,y) memcpy(x,y,sizeof(y))
using namespace std;
#define gamma 0.5772156649015328606065120
#define MOD 1000000007
#define inf 0x3f3f3f3f
#define N 100005
#define maxn 30010
typedef pair<int,int> PII;
typedef long long LL;
LL read(){
    LL x=0,f=1;char ch=getchar();
    while(ch<‘0‘||ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
    while(ch>=‘0‘&&ch<=‘9‘){x=(x<<3)+(x<<1)+ch-‘0‘;ch=getchar();}
    return x*f;
}
int n,m,k,sz,L,R;
int a[N],mrk[N<<2];
struct Seg{int l,r,v;}seg[N<<2];
int son[N],siz[N],id[N],tid,posi[N];
int top[N],fa[N],dep[N],head[N],hcnt;
struct Node{int to,nxt;}node[N<<1];
void dfs1(int u,int f,int deep){
    dep[u]=deep,fa[u]=f,siz[u]=1;
    for(int i=head[u];~i;i=node[i].nxt){
        int e=node[i].to;
        if(e==f)continue;
        dfs1(e,u,deep+1);
        siz[u]+=siz[e];
        if(!son[u]||siz[son[u]]<siz[e])
            son[u]=e;
    }
}
void dfs2(int u,int tp){
    top[u]=tp,id[u]=++tid,posi[tid]=u;
    if(!son[u])return;dfs2(son[u],tp);
    for(int i=head[u];~i;i=node[i].nxt){
        int e=node[i].to;
        if(!id[e])dfs2(e,e);
    }
}
void pushdown(int rt){
    seg[rt<<1].v=seg[rt<<1|1].v=1;
    seg[rt<<1].l=seg[rt<<1].r=mrk[rt];
    seg[rt<<1|1].l=seg[rt<<1|1].r=mrk[rt];
    mrk[rt<<1]=mrk[rt<<1|1]=mrk[rt];mrk[rt]=-1;
}
int query(int rt,int l,int r){
    if(L<=l&&r<=R)return seg[rt].v;
    int mid=l+r>>1,temp=0,t1=-1,t2=-1;
    if(~mrk[rt])pushdown(rt);
    if(L<=mid)t1=seg[rt<<1].r,temp+=query(lson);
    if(R>mid) t2=seg[rt<<1|1].l,temp+=query(rson);
    seg[rt].l=seg[rt<<1].l,seg[rt].r=seg[rt<<1|1].r;
    seg[rt].v=seg[rt<<1].v+seg[rt<<1|1].v-(seg[rt<<1].r==seg[rt<<1|1].l);
    temp-=(t1==t2&&t1!=-1);
    return temp;
}
void update(int rt,int l,int r,int v){
    if(L<=l&&r<=R){seg[rt].v=1,seg[rt].l=seg[rt].r=mrk[rt]=v;return;}
    int mid=l+r>>1;
    if(~mrk[rt])pushdown(rt);
    if(L<=mid)update(lson,v);
    if(R>mid) update(rson,v);
    seg[rt].l=seg[rt<<1].l,seg[rt].r=seg[rt<<1|1].r;
    seg[rt].v=seg[rt<<1].v+seg[rt<<1|1].v-(seg[rt<<1].r==seg[rt<<1|1].l);
}
int findp(int rt,int l,int r,int L){
    if(l==r)return seg[rt].l;
    int mid=l+r>>1,temp;
    if(~mrk[rt])pushdown(rt);
    if(L<=mid)return findp(lson,L);
    else return findp(rson,L);
}
void lca(int x,int y){
    int res=0;
    while(top[x]!=top[y]){
        if(dep[top[x]]<dep[top[y]])swap(x,y);
        L=id[top[x]],R=id[x];
        res+=query(1,1,n);
        L=id[x];
        if(findp(1,1,n,id[top[x]])==findp(1,1,n,id[fa[top[x]]]))--res; ///看两端是否相同
        x=fa[top[x]];
    }
    if(dep[x]>dep[y])swap(x,y);
    L=id[x],R=id[y];
    res+=query(1,1,n);
    printf("%d\n",res);
}
void change(int x,int y,int v){
    while(top[x]!=top[y]){
        if(dep[top[x]]<dep[top[y]])swap(x,y);
        L=id[top[x]],R=id[x];
        update(1,1,n,v);
        x=fa[top[x]];
    }
    if(dep[x]>dep[y])swap(x,y);
    L=id[x],R=id[y];
    update(1,1,n,v);
}
void build(int rt,int l,int r){
    if(l==r){seg[rt].l=seg[rt].r=a[posi[l]],seg[rt].v=1;return;}
    int mid=l+r>>1;
    build(lson);build(rson);
    seg[rt].v=seg[rt<<1].v+seg[rt<<1|1].v-(seg[rt<<1].r==seg[rt<<1|1].l);
    seg[rt].l=seg[rt<<1].l,seg[rt].r=seg[rt<<1|1].r;
}
int main(){
    int i,j,group,x,y,v;
    n=read(),m=read();mst(head,-1);mst(mrk,-1);
    for(i=1;i<=n;++i)a[i]=read();
    for(i=1;i<n;++i){
        x=read(),y=read();
        node[hcnt].to=y;node[hcnt].nxt=head[x],head[x]=hcnt++;
        node[hcnt].to=x,node[hcnt].nxt=head[y],head[y]=hcnt++;
    }
    dfs1(1,1,1);dfs2(1,1);build(1,1,n);
    char ch;
    while(m--){
        scanf(" %c",&ch);
        x=read(),y=read();
        if(ch==‘Q‘) lca(x,y);
        else v=read(),change(x,y,v);
    }
    return 0;
}