BZOJ 3083 遥远的国度

Posted 2020-08-09 ziliuziliu

链剖水题。

#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#define maxv 100500
#define maxe 200500
#define inf 2147483647
using namespace std;
int n,m,type,x,y,z,val[maxv],id=1,g[maxv],nume=0;
int w[maxv],fw[maxv],dis[maxv],fath[maxv],top[maxv],size[maxv],son[maxv],mx[maxv],times=0;
int root,tot=0,ls[maxv<<2],rs[maxv<<2],mn[maxv<<2],lazy[maxv<<2];
struct edge
{
    int v,nxt;
}e[maxe];
void addedge(int u,int v)
{
    e[++nume].v=v;
    e[nume].nxt=g[u];
    g[u]=nume;
}
void dfs1(int x,int father)
{
    size[x]=1;son[x]=0;
    for (int i=g[x];i;i=e[i].nxt)
    {
        int v=e[i].v;
        if (v!=father)
        {
            fath[v]=x;dis[v]=dis[x]+1;
            dfs1(v,x);
            size[x]+=size[v];
            if (size[v]>size[son[x]]) son[x]=v;
        }
    }
}
void dfs2(int x,int father)
{
    w[x]=mx[x]=++times;fw[times]=x;top[x]=father;
    if (son[x]) {dfs2(son[x],father);mx[x]=max(mx[x],mx[son[x]]);}
    for (int i=g[x];i;i=e[i].nxt)
    {
        int v=e[i].v;
        if ((v!=fath[x]) && (v!=son[x]))
        {
            dfs2(v,v);
            mx[x]=max(mx[x],mx[v]);
        }
    }
}
void build(int &now,int left,int right)
{
    now=++tot;lazy[now]=inf;
    if (left==right)
    {
        mn[now]=val[fw[left]];
        return;
    }
    int mid=left+right>>1;
    build(ls[now],left,mid);
    build(rs[now],mid+1,right);
    mn[now]=min(mn[ls[now]],mn[rs[now]]);
}
void pushdown(int now)
{
    if (lazy[now]==inf) return;
    lazy[ls[now]]=lazy[rs[now]]=mn[ls[now]]=mn[rs[now]]=lazy[now];
    lazy[now]=inf;
}
void modify(int now,int left,int right,int l,int r,int x)
{
    pushdown(now);
    if ((left==l) && (right==r))
    {
        lazy[now]=x;mn[now]=x;
        return;
    }
    int mid=left+right>>1;
    if (r<=mid) modify(ls[now],left,mid,l,r,x);
    else if (l>=mid+1) modify(rs[now],mid+1,right,l,r,x);
    else
    {
        modify(ls[now],left,mid,l,mid,x);
        modify(rs[now],mid+1,right,mid+1,r,x);
    }
    mn[now]=min(mn[ls[now]],mn[rs[now]]);
}
void line_modify()
{
    int f1=top[x],f2=top[y];
    while (f1!=f2)
    {
        if (dis[f1]<dis[f2]) {swap(f1,f2);swap(x,y);}
        modify(root,1,n,w[f1],w[x],z);
        x=fath[f1];f1=top[x];
    }
    if (dis[x]>dis[y]) swap(x,y);
    modify(root,1,n,w[x],w[y],z);
}
int lca(int x,int y)
{
    int f1=top[x],f2=top[y];
    while (f1!=f2)
    {
        if (dis[f1]<dis[f2]) {swap(f1,f2);swap(x,y);}
        x=fath[f1];f1=top[x];
    }
    if (dis[x]<dis[y]) return x;
    return y;
}
int lca2(int x,int pos)
{
    int f1=top[x],f2=top[pos],ret;
    while (f1!=f2) {ret=f1;x=fath[f1];f1=top[x];}
    if (x==pos) return ret;
    else return son[pos];
}
int ask(int now,int left,int right,int l,int r)
{
    if (l>r) return inf;
    pushdown(now);
    if ((left==l) && (right==r))
        return mn[now];
    int mid=left+right>>1;
    if (r<=mid) return ask(ls[now],left,mid,l,r);
    else if (l>=mid+1) return ask(rs[now],mid+1,right,l,r);
    else return min(ask(ls[now],left,mid,l,mid),ask(rs[now],mid+1,right,mid+1,r));
}
void line_ask()
{
    int t=lca(id,x);
    if (id==x)
        printf("%d\n",ask(root,1,n,1,n));
    else if (t==x)
    {
        int pos=lca2(id,x);
        int l=w[pos]-1,r=mx[pos]+1;
        printf("%d\n",min(ask(root,1,n,1,l),ask(root,1,n,r,n)));
    }
    else
        printf("%d\n",ask(root,1,n,w[x],mx[x]));
}
int main()
{
    scanf("%d%d",&n,&m);
    for (int i=1;i<=n-1;i++)
    {
        scanf("%d%d",&x,&y);
        addedge(x,y);addedge(y,x);
    }
    for (int i=1;i<=n;i++) scanf("%d",&val[i]);
    scanf("%d",&id);
    dfs1(1,1);
    dfs2(1,1);
    build(root,1,n);
    for (int i=1;i<=m;i++)
    {
        scanf("%d",&type);
        if (type==1) scanf("%d",&id);
        else if (type==2)
        {
            scanf("%d%d%d",&x,&y,&z);
            line_modify();
        }
        else
        {
            scanf("%d",&x);
            line_ask();
        }
    }
    return 0;
}