题面
题解
线段树+树链剖分大水题
维护颜色段的方法很简单呀。。。
维护当前区间内的颜色段个数，
以及当前区间左端和右端的颜色，
合并的时候考虑是否要减一下就行了
至于跳LCA进行Modify的时候稍微注意一下细节
#include<iostream>
#include<cstdio>
#include<cstdlib>
#include<cstring>
#include<cmath>
#include<algorithm>
#define MAX 110000
#define lson (now<<1)
#define rson (now<<1|1)
using namespace std;
inline int read()
{
register int x=0,t=1;
register char ch=getchar();
while((ch<'0'||ch>'9')&&ch!='-')ch=getchar();
if(ch=='-'){t=-1;ch=getchar();}
while(ch>='0'&&ch<='9'){x=x*10+ch-48;ch=getchar();}
return x*t;
}
struct Line
{
int v,next;
}e[MAX<<1];
int h[MAX],cnt=1;
struct Node
{
int c;
int lc,rc;
int ly;
}t[MAX<<2];
inline void Add(int u,int v)
{
e[cnt]=(Line){v,h[u]};
h[u]=cnt++;
}
int n,m,c[MAX],tim;
int dfn[MAX],dep[MAX],line[MAX],ff[MAX],size[MAX],hson[MAX],top[MAX];
void dfs1(int u,int fa)
{
size[u]=1;dep[u]=dep[fa]+1;
for(int i=h[u];i;i=e[i].next)
{
int v=e[i].v;
if(v==fa)continue;
ff[v]=u;
dfs1(v,u);
size[u]+=size[v];
if(size[v]>size[hson[u]])hson[u]=v;
}
}
void dfs2(int u,int tp)
{
top[u]=tp;dfn[u]=++tim;line[tim]=u;
if(hson[u])dfs2(hson[u],tp);
for(int i=h[u];i;i=e[i].next)
{
int v=e[i].v;
if(v==hson[u]||v==ff[u])continue;
dfs2(v,v);
}
}
void pushup(int now)
{
t[now].c=t[lson].c+t[rson].c;
if(t[lson].rc==t[rson].lc)t[now].c--;
t[now].lc=t[lson].lc;
t[now].rc=t[rson].rc;
}
void pushdown(int now)
{
if(t[now].ly)
{
t[lson].ly=t[rson].ly=t[lson].lc=t[now].ly;
t[rson].lc=t[lson].rc=t[rson].rc=t[now].ly;
t[lson].c=t[rson].c=1;
t[now].ly=0;
}
}
void putlazy(int now,int ly)
{
t[now].c=1;
t[now].lc=t[now].rc=ly;
t[now].ly=ly;
}
void Build(int now,int l,int r)
{
if(l==r)
{
t[now].lc=t[now].rc=c[line[l]];
t[now].c=1;
return;
}
int mid=(l+r)>>1;
Build(lson,l,mid);Build(rson,mid+1,r);
pushup(now);
t[now].lc=t[lson].lc;
t[now].rc=t[rson].rc;
}
int getl(int now,int l,int r,int al)
{
if(al==l)return t[now].lc;
pushdown(now);
int mid=(l+r)>>1;
int re;
if(mid>=al)re=getl(lson,l,mid,al);
else re=getl(rson,mid+1,r,al);
pushup(now);
return re;
}
int getr(int now,int l,int r,int ar)
{
if(r==ar)return t[now].rc;
pushdown(now);
int mid=(l+r)>>1;
int re;
if(mid>=ar)re=getr(lson,l,mid,ar);
else re=getr(rson,mid+1,r,ar);
pushup(now);
return re;
}
int Query(int now,int l,int r,int al,int ar)
{
if(l==al&&r==ar)return t[now].c;
pushdown(now);
int mid=(l+r)>>1;
int re;
if(ar<=mid)re=Query(lson,l,mid,al,ar);
else if(al>mid)re=Query(rson,mid+1,r,al,ar);
else re=(Query(lson,l,mid,al,mid)+Query(rson,mid+1,r,mid+1,ar)-(t[lson].rc==t[rson].lc?1:0));
return re;
}
void Modify(int now,int l,int r,int al,int ar,int cc)
{
if(l==al&&r==ar)
{
putlazy(now,cc);return;
}
int mid=(l+r)>>1;
pushdown(now);
if(ar<=mid)Modify(lson,l,mid,al,ar,cc);
else if(al>mid)Modify(rson,mid+1,r,al,ar,cc);
else
{
Modify(lson,l,mid,al,mid,cc);
Modify(rson,mid+1,r,mid+1,ar,cc);
}
pushup(now);
}
int Answer(int u,int v)
{
int ans=0;
int lu=-1,lv=-1;
while(top[u]!=top[v])
{
if(dep[top[u]]<dep[top[v]])swap(u,v),swap(lu,lv);
int cl=getl(1,1,n,dfn[top[u]]),cr=getr(1,1,n,dfn[u]);
ans+=Query(1,1,n,dfn[top[u]],dfn[u]);
if(cr==lu)ans--;
lu=cl;
u=ff[top[u]];
}
if(dep[u]>dep[v])swap(u,v),swap(lu,lv);
ans+=Query(1,1,n,dfn[u],dfn[v]);
int cl=getl(1,1,n,dfn[u]),cr=getr(1,1,n,dfn[v]);
if(cl==lu)--ans;
if(cr==lv)--ans;
return ans;
}
void Change(int u,int v,int cc)
{
while(top[u]!=top[v])
{
if(dep[top[u]]<dep[top[v]])swap(u,v);
Modify(1,1,n,dfn[top[u]],dfn[u],cc);
u=ff[top[u]];
}
if(dep[u]>dep[v])swap(u,v);
Modify(1,1,n,dfn[u],dfn[v],cc);
}
int main()
{
n=read();m=read();
for(int i=1;i<=n;++i)c[i]=read();
for(int i=1;i<n;++i)
{
int u=read(),v=read();
Add(u,v);Add(v,u);
}
dfs1(1,0);dfs2(1,1);
Build(1,1,n);
char ch[5];
while(m--)
{
scanf("%s",ch);
if(ch[0]=='C')
{
int a=read(),b=read(),c=read();
Change(a,b,c);
}
else
{
int a=read(),b=read();
printf("%d\n",Answer(a,b));
}
}
return 0;
}