【Luogu】P2486染色（树链剖分）

　　题目链接

　　线段树维护左端颜色，右端颜色，颜色段数量。

　　合并的时候看左子树的右端颜色是不是等于右子树的左端颜色，如果等于那么颜色段数量要-1S

　　然后在树剖跳链的时候搞同样的操作qwq

　　然后就没有然后了

　　

#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cctype>
#include<cstdlib>
#define maxn 500000
#define left (rt<<1)
#define right (rt<<1|1)
#define mid ((l+r)>>1)
#define lson l,mid,left
#define rson mid+1,r,right
using namespace std;
inline long long read(){
    long long num=0,f=1;
    char ch=getchar();
    while(!isdigit(ch)){
        if(ch=='-')    f=-1;
        ch=getchar();
    }
    while(isdigit(ch)){
        num=num*10+ch-'0';
        ch=getchar();
    }
    return num*f;
}

int n,m;
int tag[maxn*2];
int deep[maxn];
int dfn[maxn],ID;
int back[maxn];
int q[maxn];
int son[maxn];
int top[maxn];
int father[maxn];
int size[maxn];

struct Edge{
    int next,to;
}edge[maxn*2];
int head[maxn],num;
inline void add(int from,int to){
    edge[++num]=(Edge){head[from],to};
    head[from]=num;
}

struct Node{
    int lcol,rcol,ncol;
    Node operator +(const Node a){
        Node ans=(Node){lcol,a.rcol,ncol+a.ncol};
        if(rcol==a.lcol)    ans.ncol--;
        return ans;
    }
}tree[maxn*2];

inline void pushup(int rt){
    tree[rt]=tree[left]+tree[right];
}

inline void pushdown(int rt){
    if(tag[rt]==0)    return;
    tag[left]=tag[right]=tag[rt];
    tree[left].lcol=tree[right].lcol=tree[left].rcol=tree[right].rcol=tag[rt];
    tree[left].ncol=tree[right].ncol=1;
    tag[rt]=0;
}

void build(int l,int r,int rt){
    if(l==r){
        int last=back[l];
        tree[rt]=(Node){q[last],q[last],1};
        return;
    }
    build(lson);
    build(rson);
    pushup(rt);
}

void update(int from,int to,int num,int l,int r,int rt){
    if(from<=l&&to>=r){
        tree[rt]=(Node){num,num,1};
        tag[rt]=num;
        return;
    }
    pushdown(rt);
    if(from<=mid)    update(from,to,num,lson);
    if(to>mid)        update(from,to,num,rson);
    pushup(rt);
    return;
}

int query(int from,int to,int l,int r,int rt){
    if(from<=l&&to>=r)    return tree[rt].ncol;
    pushdown(rt);
    int ans=0;
    if(from<=mid)    ans+=query(from,to,lson);
    if(to>mid)        ans+=query(from,to,rson);
    if(from<=mid&&to>mid)
        if(tree[left].rcol==tree[right].lcol)    ans--;
    return ans;
}

int qucol(int o,int l,int r,int rt){
    if(l==r)    return tree[rt].lcol;
    pushdown(rt);
    if(o<=mid)    return qucol(o,lson);
    else        return qucol(o,rson);
}

void findfs(int x,int fa){
    deep[x]=deep[fa]+1;    size[x]=1;    father[x]=fa;
    for(int i=head[x];i;i=edge[i].next){
        int to=edge[i].to;
        if(to==fa)    continue;
        findfs(to,x);
        size[x]+=size[to];
        if(son[x]==0||size[son[x]]<size[to])    son[x]=to;
    }
}

void unidfs(int x,int Top){
    top[x]=Top;
    dfn[x]=++ID;    back[ID]=x;
    if(son[x]==0)    return;
    unidfs(son[x],Top);
    for(int i=head[x];i;i=edge[i].next){
        int to=edge[i].to;
        if(to==father[x]||to==son[x])    continue;
        unidfs(to,to);
    }
}

void uplink(int from,int to,int num){
    while(top[from]!=top[to]){
        if(deep[top[from]]<deep[top[to]])    swap(from,to);
        update(dfn[top[from]],dfn[from],num,1,n,1);
        from=father[top[from]];
    }
    if(deep[from]>deep[to])    swap(from,to);
    update(dfn[from],dfn[to],num,1,n,1);
}

int qulink(int from,int to){
    int ans=0;
    while(top[from]!=top[to]){
        if(deep[top[from]]<deep[top[to]])    swap(from,to);
        ans+=query(dfn[top[from]],dfn[from],1,n,1);
        from=top[from];
        if(qucol(dfn[from],1,n,1)==qucol(dfn[father[from]],1,n,1))    ans--;
        from=father[from];
    }
    if(deep[from]>deep[to])    swap(from,to);
    ans+=query(dfn[from],dfn[to],1,n,1);
    return ans;
}

int main(){
    n=read(),m=read();
    for(int i=1;i<=n;++i)    q[i]=read();
    for(int i=1;i<n;++i){
        int from=read(),to=read();
        add(from,to);
        add(to,from);
    }
    findfs(1,1);
    unidfs(1,1);
    build(1,n,1);
    for(int i=1;i<=m;++i){
        char ch[10];    int a,b;
        scanf("%s%d%d",ch,&a,&b);
        if(ch[0]=='Q')    printf("%d
",qulink(a,b));
        else if(ch[0]=='C'){
            int c=read();
            uplink(a,b,c);
        }
    }
    return 0;
}