树链剖分裸题,建线段树的时候维护左端点右端点然后合并信息的时候中间相同的话减1,注意在树链剖分的时候也是如此
这道题调了好久,一定要注意在树链剖分时每个点的位置是用num数组存储的,所以每次query或者change的时候都一定要用num[]来表示节点,而不是直接用节点表示
#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<algorithm>
using namespace std;
const int N=100010;
int qx,n,m,te,sz;
int tp[N],head[N],num[N],val[N],tree[N],h[N],fa[N],son[N],size[N];
struct seg{
int l,r,sum,tag,lcol,rcol;
}tr[400010];
struct edge{
int v,next;
}e[200010];
inline int F()
{
register int aa,bb;register char ch;
while(ch=getchar(),(ch<'0'||ch>'9')&&ch!='-');ch=='-'?aa=bb=0:(aa=ch-'0',bb=1);
while(ch=getchar(),ch>='0'&&ch<='9')aa=(aa<<3)+(aa<<1)+ch-'0';return bb?aa:-aa;
}
void clear()
{
sz=te=0;memset(head,0,sizeof(head));
h[1]=fa[1]=1;size[0]=0;
memset(son,0,sizeof(son));
}
void add(int u,int v)
{
e[++te].v=v;
e[te].next=head[u];
head[u]=te;
}
void pushdown(int k)
{
if (tr[k].tag==-1||tr[k].l==tr[k].r)return;
tr[k<<1].lcol=tr[k<<1].rcol=tr[k<<1|1].lcol=tr[k<<1|1].rcol=tr[k].tag;
tr[k<<1].sum=tr[k<<1|1].sum=1;
tr[k<<1].tag=tr[k<<1|1].tag=tr[k].tag;
tr[k].tag=-1;
}
void updata(int k)
{
tr[k].lcol=tr[k<<1].lcol,tr[k].rcol=tr[k<<1|1].rcol;
tr[k].sum=tr[k<<1].sum+tr[k<<1|1].sum;
if (tr[k<<1].rcol==tr[k<<1|1].lcol)tr[k].sum--;
}
void dfs1(int x)
{
size[x]=1;
for (int i=head[x];i;i=e[i].next)
{
int v=e[i].v;
if (v==fa[x])continue;
fa[v]=x;
h[v]=h[x]+1;
dfs1(v);
size[x]+=size[v];
if (size[v]>size[son[x]])son[x]=v;
}
}
void dfs2(int x,int chain)
{
tp[x]=chain;
num[x]=++sz;
if (!son[x])return ;
dfs2(son[x],chain);
for (int i=head[x];i;i=e[i].next)
{
int v=e[i].v;
if (v==fa[x]||v==son[x])continue;
dfs2(v,v);
}
}
void build(int k,int l,int r)
{
tr[k].l=l;tr[k].r=r;tr[k].tag=-1;
if (l==r)
{
tr[k].lcol=tr[k].rcol=tree[l];
tr[k].sum=1;return;
}
int mid=(l+r)>>1;
build(k<<1,l,mid);
build(k<<1|1,mid+1,r);
updata(k);
}
void change(int k,int x,int y,int z)
{
int l=tr[k].l,r=tr[k].r;
if (x<=l&&r<=y)
{
tr[k].lcol=tr[k].rcol=tr[k].tag=z;
tr[k].sum=1;return;
}
pushdown(k);
int mid=(l+r)>>1;
if (x<=mid)change(k<<1,x,y,z);
if (y>mid)change(k<<1|1,x,y,z);
updata(k);
}
int queryx(int k,int x)
{
int l=tr[k].l,r=tr[k].r;
if (l==r)
{
return tr[k].lcol;
}
pushdown(k);
int mid=(l+r)>>1;
if (x<=mid)return queryx(k<<1,x);
if (x>mid)return queryx(k<<1|1,x);
updata(k);
}
void querysum(int k,int x,int y)
{
int l=tr[k].l,r=tr[k].r;
if (x<=l&&r<=y)
{
qx+=tr[k].sum;return;
}
pushdown(k);
int mid=(l+r)>>1;
if (x<=mid)querysum(k<<1,x,y);
if (y>mid)querysum(k<<1|1,x,y);
if (x<=mid&&y>mid&&tr[k<<1].rcol==tr[k<<1|1].lcol)qx--;
updata(k);
}
void solvechange(int x,int y,int z)
{
while (tp[x]!=tp[y])
{
if (h[tp[x]]<h[tp[y]])swap(x,y);
change(1,num[tp[x]],num[x],z);
x=fa[tp[x]];
}
if (num[x]>num[y])swap(x,y);
change(1,num[x],num[y],z);
}
void solvesum(int x,int y)
{
qx=0;
while(tp[x]!=tp[y])
{
if (h[tp[x]]<h[tp[y]])swap(x,y);
querysum(1,num[tp[x]],num[x]);
int a1=queryx(1,num[tp[x]]),a2=queryx(1,num[fa[tp[x]]]);
// cout<<a1<<' '<<a2<<' '<<qx<<endl;
if (a1==a2)qx--;
x=fa[tp[x]];
}
if (num[x]>num[y])swap(x,y);
querysum(1,num[x],num[y]);
}
int main()
{
// freopen("std.in","r",stdin);
clear();
int u,v,x,y,z;
n=F(),m=F();
for (int i=1;i<=n;++i)val[i]=F();
for (int i=1;i<n;++i)
{
u=F(),v=F();
add(u,v),add(v,u);
}
dfs1(1),dfs2(1,1);
for (int i=1;i<=n;++i)tree[num[i]]=val[i];
// for (int i=1;i<=n;i++)cout<<num[i]<<' ';
// cout<<endl;
build(1,1,n);
// for (int i=1;i<=20;++i)
// cout<<tr[i].l<<' '<<tr[i].r<<' '<<tr[i].lcol<<' '<<tr[i].rcol<<' '<<tr[i].sum<<endl;
char s[4];
for (int i=1;i<=m;++i)
{
scanf("%s",s);
if (s[0]=='Q')
{
x=F(),y=F();
solvesum(x,y);
// if (i==7)
// for (int i=1;i<=20;++i)cout<<tr[i].l<<' '<<tr[i].r<<' '<<tr[i].lcol<<' '<<tr[i].rcol<<' '<<tr[i].sum<<endl;
printf("%d\n",qx);
}
else
{
x=F(),y=F(),z=F();
solvechange(x,y,z);
}
}
}