树链剖分题
将树剖分后维护区间首尾的颜色
区间合并的时候若左区间尾颜色==右区间首颜色，则a[n].num=a[lch].num+a[rch].num-1;否则a[n].num=a[lch].num+a[rch].num；
然后就是注意在重链上跳累加答案的时候判一下该重链头和其父亲的颜色是否一致，一致的话sum--
/**************************************************************
Problem: 2243
User: syh0313
Language: C++
Result: Accepted
Time:4928 ms
Memory:33808 kb
****************************************************************/
#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <string>
#define lch a[n].lc
#define rch a[n].rc
using namespace std;
const int maxn=2e5;
int n,m,v[maxn],st[maxn],to[maxn],nt[maxn],topt,cnt,root;
int dep[maxn],fa[maxn],rem[maxn],si[maxn];
int dfn_num,dfn[maxn],line[maxn],top[maxn];
bool f[maxn];
char s[maxn];
struct da{int lc,rc,num,head,tail,tag;}a[maxn<<2];
void add(int x,int y)
{to[++topt]=y; nt[topt]=st[x]; st[x]=topt;}
void dfs1(int x,int de)
{
dep[x]=de; f[x]=1; si[x]=1; int p=st[x],ma=0;
while (p)
{
if (!f[to[p]])
{
dfs1(to[p],de+1);
fa[to[p]]=x; si[x]+=si[to[p]];
if (si[to[p]]>ma) {ma=si[to[p]]; rem[x]=to[p];}
}
p=nt[p];
}
}
void dfs2(int x)
{
f[x]=1; if (rem[fa[x]]==x) top[x]=top[fa[x]];else top[x]=x;
dfn[x]=++dfn_num; line[dfn_num]=x; int p=st[x];
if (rem[x]) dfs2(rem[x]);
while (p)
{
if (!f[to[p]]) dfs2(to[p]);
p=nt[p];
}
}
void updata(int n)
{
if (a[lch].tail==a[rch].head) a[n].num=a[lch].num+a[rch].num-1;
else a[n].num=a[lch].num+a[rch].num;
a[n].head=a[lch].head; a[n].tail=a[rch].tail;
}
void build_tree(int &n,int l,int r)
{
n=++topt;
if (l==r)
{a[n].num=1; a[n].head=v[line[l]]; a[n].tail=v[line[l]]; return;}
int mid=(l+r)>>1;
build_tree(lch,l,mid); build_tree(rch,mid+1,r);
updata(n);
}
void pushdown(int n)
{
if (!a[n].tag) return;
a[lch].num=a[rch].num=1;
a[lch].head=a[lch].tail=a[rch].head=a[rch].tail=a[n].tag;
a[lch].tag=a[rch].tag=a[n].tag;
a[n].tag=0;
}
void tree_fz(int n,int L,int R,int l,int r,int k)
{
if (L==l && R==r)
{
a[n].tag=k; a[n].num=1; a[n].head=k; a[n].tail=k;
return;
}
pushdown(n);
int mid=(L+R)>>1;
if (r<=mid) tree_fz(lch,L,mid,l,r,k);
else if (l>=mid+1) tree_fz(rch,mid+1,R,l,r,k);
else tree_fz(lch,L,mid,l,mid,k),tree_fz(rch,mid+1,R,mid+1,r,k);
updata(n);
}
void qfz(int x,int y,int k)
{
while (top[x]!=top[y])
{
if (dep[top[x]]<dep[top[y]]) swap(x,y);
tree_fz(root,1,n,dfn[top[x]],dfn[x],k);
x=fa[top[x]];
}
if (dfn[x]>dfn[y]) swap(x,y);
tree_fz(root,1,n,dfn[x],dfn[y],k);
return;
}
int qury(int n,int L,int R,int l,int r)
{
if (L==l && R==r) return a[n].num;
pushdown(n);
int mid=(L+R)>>1;
if (r<=mid) return qury(lch,L,mid,l,r);
else if (l>=mid+1) return qury(rch,mid+1,R,l,r);
else
{
if (a[lch].tail==a[rch].head)
return qury(lch,L,mid,l,mid)+qury(rch,mid+1,R,mid+1,r)-1;
return qury(lch,L,mid,l,mid)+qury(rch,mid+1,R,mid+1,r);
}
updata(n);
}
int qcol(int n,int l,int r,int lc)
{
if (l==r && l==lc) return a[n].head;
pushdown(n);
int mid=(l+r)>>1;
if (lc<=mid) return qcol(lch,l,mid,lc);
else return qcol(rch,mid+1,r,lc);
updata(n);
}
int qsum(int x,int y)
{
int sum=0;
while (top[x]!=top[y])
{
if (dep[top[x]]<dep[top[y]]) swap(x,y);
sum+=qury(root,1,n,dfn[top[x]],dfn[x]);
if (qcol(root,1,n,dfn[fa[top[x]]])==qcol(root,1,n,dfn[top[x]]))
sum--;
x=fa[top[x]];
}
if (dfn[x]>dfn[y]) swap(x,y);
sum+=qury(root,1,n,dfn[x],dfn[y]);
return sum;
}
int main()
{
scanf("%d%d",&n,&m);
for (int i=1;i<=n;i++) scanf("%d",&v[i]);
for (int i=1;i<n;i++)
{
int xx,yy; scanf("%d%d",&xx,&yy);
add(xx,yy); add(yy,xx);
}
dfs1(1,1); memset(f,0,sizeof f); dfs2(1);
build_tree(root,1,n);
for (int i=1;i<=m;i++)
{
int l,r,xx; scanf("%s%d%d",s,&l,&r);
if (s[0]=='Q') printf("%d\n",qsum(l,r));
else scanf("%d",&xx),qfz(l,r,xx);
}
return 0;
}