【树链剖分+dfs序】【bzoj 3083】: 遥远的国度

http://www.lydsy.com/JudgeOnline/problem.php?id=3083

维护轻重链剖分得到的dfs序即可

#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <iostream>
#include <cmath>
#include <algorithm>
using namespace std;
#define rep(i,l,r) for(int i=(l),_=(r);i<=_;i++)
#define per(i,r,l) for(int i=(r),_=(l);i>=_;i--)
#define MS(arr,x) memset(arr,x,sizeof(arr))
#define INE(i,u) for(int i=head[u];~i;i=e[i].next)
#define LL long long
inline const int read()
{int r=0,k=1;char c=getchar();for(;c<'0'||c>'9';c=getchar())if(c=='-')k=-1;
for(;c>='0'&&c<='9';c=getchar())r=r*10+c-'0';return k*r;}
////////////////////////////////////////////////
const int inf=0x7fffffff;
const int N=100010;
int n,q;
int w
;
struct edge{int v,next;}e[N*2];
int head
,k;
int fa
[18],dep
,sz
,son
;
int top
;
int root;
int in
,out
,dfs_clock;
int mi[540000],lz[540000];
////////////////////////////////////////////////
void adde(int u,int v){e[k]=(edge){v,head[u]};head[u]=k++;}
void dfs1(int u)
{
sz[u]=1;
INE(i,u)
{
int v=e[i].v; if(v==fa[u][0]) continue;
fa[v][0]=u; dep[v]=dep[u]+1; rep(i,1,17) fa[v][i]=fa[fa[v][i-1]][i-1];
dfs1(v);
sz[u]+=sz[v];
if(sz[son[u]] < sz[v]) son[u]=v;
}
}
void dfs2(int u,int tp)
{
in[u]=++dfs_clock; top[u]=tp;
if(son[u]) dfs2(son[u],tp);
INE(i,u)
{
int v=e[i].v; if(v==fa[u][0] || v==son[u]) continue;
dfs2(v,v);
}
out[u]=++dfs_clock;
}
int getanc(int u,int d)
{
d=dep[u]-d;
rep(i,0,17) if(d&(1<<i)) u=fa[u][i];
return u;
}
#define LS o<<1,L,mid
#define RS o<<1|1,mid+1,R
void modify(int l,int r,int x,int o,int L,int R)
{
if(l<=L && R<=r)
{
lz[o]=mi[o]=x;
return;
}
if(lz[o]) lz[o<<1]=lz[o<<1|1]=mi[o<<1]=mi[o<<1|1]=lz[o],lz[o]=0;
int mid=L+R>>1;
if(r<=mid) modify(l,r,x,LS);
else if(l>mid) modify(l,r,x,RS);
else modify(l,mid,x,LS), modify(mid+1,r,x,RS);
mi[o]=min(mi[o<<1],mi[o<<1|1]);
}
int getmin(int l,int r,int o,int L,int R)
{
if(l<=L && R<=r) return mi[o];
if(lz[o]) lz[o<<1]=lz[o<<1|1]=mi[o<<1]=mi[o<<1|1]=lz[o],lz[o]=0;
int mid=L+R>>1;
if(r<=mid) return getmin(l,r,LS);
else if(l>mid) return getmin(l,r,RS);
else return min(getmin(l,mid,LS),getmin(mid+1,r,RS));
}
void modify(int a,int b,int x)
{
for(int ta=top[a],tb=top[b];ta!=tb;a=fa[ta][0],ta=top[a])
{
if(dep[ta] < dep[tb]) swap(a,b),swap(ta,tb);
modify(in[ta],in[a],x,1,1,2*n);
}
if(dep[a] > dep[b]) swap(a,b);
modify(in[a],in[b],x,1,1,2*n);
}
////////////////////////////////////////////////
void input()
{
MS(head,-1);
n=read(); q=read();
rep(i,2,n)
{
int u=read(),v=read();
adde(u,v); adde(v,u);
}
rep(i,1,n) w[i]=read();
root=read();
}
void solve()
{
int op,x,y,z;
dfs1(root);
dfs2(root,root);
rep(i,1,n) modify(out[i],out[i],inf,1,1,2*n);
rep(i,1,n) modify(in[i],in[i],w[i],1,1,2*n);
while(q--)
{
op=read();
if(op==1) root=read();
else if(op==2)
{
x=read(); y=read(); z=read();
modify(x,y,z);
}
else
{
x=read();
if(x==root) printf("%d\n",getmin(1,2*n,1,1,2*n));
else if(dep[x] < dep[root] && getanc(root,dep[x]) == x)
{
x=getanc(root,dep[x]+1);
int ans=getmin(1,in[x]-1,1,1,2*n);
ans=min(ans,getmin(out[x]+1,2*n,1,1,2*n));
printf("%d\n",ans);
}
else printf("%d\n",getmin(in[x],out[x],1,1,2*n));
}
}
}
////////////////////////////////////////////////
int main()
{
freopen("std.in","r",stdin); freopen("std.out","w",stdout);
input(),solve();
return 0;
}