解题： SDOI 2011 染色

题面

强行把序列问题通过树剖套在树上。。。算了算是回顾了一下树剖的思想=。=

每次树上跳的时候注意跳的同时维护当前拼出来的左右两条链的靠上的端点，然后拼起来的时候讨论一下拼接点，最后一下左右两边的端点都要考虑

 #include<cstdio>
 #include<cstring>
 #include<algorithm>
 using namespace std;
 const int N=;
 struct a
 {
     int cnt;
     int lc,rc;
 };
 int num[N],nmb[N],val[*N],lcol[*N],rcol[*N],laz[*N];
 int siz[N],dep[N],anc[N],imp[N],top[N],dfn[N];
 int p[N],noww[*N],goal[*N];
 int n,m,t1,t2,t3,cnt,tot;
 char rd[];
 void link(int f,int t)
 {
     noww[++cnt]=p[f];
     goal[cnt]=t,p[f]=cnt;
 }
 void DFS(int nde,int fth,int dth)
 {
     int tmp=;
     siz[nde]=,anc[nde]=fth,dep[nde]=dth;
     for(int i=p[nde];i;i=noww[i])
         if(goal[i]!=fth)
         {
             DFS(goal[i],nde,dth+);
             siz[nde]+=siz[goal[i]];
             if(siz[goal[i]]>tmp)
                 tmp=siz[goal[i]],imp[nde]=goal[i];
         }
 }
 void MARK(int nde,int tpp)
 {
     dfn[nde]=++tot,nmb[tot]=num[nde],top[nde]=tpp;
     if(imp[nde])
     {
         MARK(imp[nde],tpp);
         for(int i=p[nde];i;i=noww[i])
             if(goal[i]!=anc[nde]&&goal[i]!=imp[nde])
                 MARK(goal[i],goal[i]);
     }
 }
 void pushup(int nde)
 {
     int ls=*nde,rs=*nde+;
     lcol[nde]=lcol[ls],rcol[nde]=rcol[rs];
     val[nde]=val[ls]+val[rs]-(rcol[ls]==lcol[rs]);
 }
 void create(int nde,int l,int r)
 {
     if(l==r)
         val[nde]=,lcol[nde]=rcol[nde]=nmb[l];
     else
     {
         int mid=(l+r)/,ls=*nde,rs=*nde+;
         create(ls,l,mid),create(rs,mid+,r);
         pushup(nde);
     }
 }
 void release(int nde,int l,int r)
 {
     if(laz[nde])
     {
         int ls=*nde,rs=*nde+;
         laz[ls]=lcol[ls]=rcol[ls]=laz[nde];
         laz[rs]=lcol[rs]=rcol[rs]=laz[nde];
         val[ls]=val[rs]=; laz[nde]=;
     }
 }
 void change(int nde,int l,int r,int nl,int nr,int task)
 {
     if(l>nr||r<nl)
         return ;
     else if(l>=nl&&r<=nr)
         val[nde]=,lcol[nde]=rcol[nde]=laz[nde]=task;
     else
     {
         int mid=(l+r)/,ls=*nde,rs=*nde+; release(nde,l,r);
         change(ls,l,mid,nl,nr,task),change(rs,mid+,r,nl,nr,task);
         pushup(nde);
     }
 }
 a query(int nde,int l,int r,int nl,int nr)
 {
     if(l>=nl&&r<=nr)
         return (a){val[nde],lcol[nde],rcol[nde]};
     else
     {
         int mid=(l+r)/,ls=*nde,rs=*nde+; release(nde,l,r);
         if(nr<=mid) return query(ls,l,mid,nl,nr);
         if(nl>mid) return query(rs,mid+,r,nl,nr);
         a r1=query(ls,l,mid,nl,nr),r2=query(rs,mid+,r,nl,nr),ret;
         ret.lc=r1.lc,ret.rc=r2.rc,ret.cnt=r1.cnt+r2.cnt-(r1.rc==r2.lc);
         return ret;
     }
 }
 void path_change(int x,int y,int v)
 {
     while(top[x]!=top[y])
     {
         if(dep[top[x]]<dep[top[y]]) swap(x,y);
         change(,,n,dfn[top[x]],dfn[x],v); x=anc[top[x]];
     }
     if(dep[x]>dep[y]) swap(x,y);
     change(,,n,dfn[x],dfn[y],v); return ;
 }
 int path_query(int x,int y)
 {
     int rt=,ll=-,rr=-;
     while(top[x]!=top[y])
     {
         if(dep[top[x]]<dep[top[y]]) swap(x,y),swap(ll,rr);
         a ret=query(,,n,dfn[top[x]],dfn[x]); x=anc[top[x]];
         rt+=ret.cnt-(ll==ret.rc); ll=ret.lc;
     }
     if(dep[x]>dep[y]) swap(x,y),swap(ll,rr);
     a ret=query(,,n,dfn[x],dfn[y]); rt+=ret.cnt-(ll==ret.lc)-(rr==ret.rc);
     return rt;
 }
 int main ()
 {
     scanf("%d%d",&n,&m);
     for(int i=;i<=n;i++)
         scanf("%d",&num[i]);
     for(int i=;i<n;i++)
         scanf("%d%d",&t1,&t2),link(t1,t2),link(t2,t1);
     DFS(,,); MARK(,); create(,,n);
     while(m--)
     {
         scanf("%s",rd);
         if(rd[]=='C')
             scanf("%d%d%d",&t1,&t2,&t3),path_change(t1,t2,t3);
         else
             scanf("%d%d",&t1,&t2),printf("%d\n",path_query(t1,t2));
     }
     return ;
 }