BZOJ 5507: [gzoi2019]旧词 LCT

和之前那个 【LNOI】LCA 几乎是同一道题，就是用动态树来维护查分就行.

code:

#include <bits/stdc++.h>
using namespace std;
#define N 50006
#define mod 998244353
#define ll long long
#define lson t[x].ch[0]
#define rson t[x].ch[1]
#define get(x) (t[t[x].f].ch[1]==x)
#define isrt(x) (!(t[t[x].f].ch[0]==x||t[t[x].f].ch[1]==x))
#define setIO(s) freopen(s".in","r",stdin)
int sta[N],hd[N],to[N],nex[N],answer[N],dep[N],n,Q,K,edges;
inline void add(int u,int v)
{
    nex[++edges]=hd[u],hd[u]=edges,to[edges]=v;
}
inline int qpow(int x,int y)
{
    int tmp=1;
    for(;y;y>>=1,x=(ll)x*x%mod)   if(y&1) tmp=(ll)tmp*x%mod;
    return tmp;
}
struct sol
{
    int y,id;
    sol(int y=0,int id=0):y(y),id(id){}
};
vector<sol>a[N];
struct node
{
    int f,rev,ch[2],add;
    ll sum1,sum2,val1,val2;
}t[N];
inline void pushup(int x)
{
    t[x].sum1=(t[lson].sum1+t[rson].sum1+t[x].val1)%mod;
    t[x].sum2=(t[lson].sum2+t[rson].sum2+t[x].val2)%mod;
}
inline void rotate(int x)
{
    int old=t[x].f,fold=t[old].f,which=get(x);
    if(!isrt(old)) t[fold].ch[t[fold].ch[1]==old]=x;
    t[old].ch[which]=t[x].ch[which^1],t[t[old].ch[which]].f=old;
    t[x].ch[which^1]=old,t[old].f=x,t[x].f=fold;
    pushup(old),pushup(x);
}
inline void mark(int x,int d)
{
    (t[x].val2+=1ll*d*t[x].val1%mod)%=mod;
    (t[x].sum2+=1ll*d*t[x].sum1%mod)%=mod;
    t[x].add+=d;
}
inline void pushdown(int x)
{
    if(x&&t[x].add)
    {
        if(lson)   mark(lson,t[x].add);
        if(rson)   mark(rson,t[x].add);
        t[x].add=0;
    }
}
void splay(int x)
{
    int v=0,u=x,fa;
    for(sta[++v]=u;!isrt(u);u=t[u].f)     sta[++v]=t[u].f;
    for(;v;--v)   pushdown(sta[v]);
    for(u=t[u].f;(fa=t[x].f)!=u;rotate(x))
    {
        if(t[fa].f!=u)
        {
            rotate(get(fa)==get(x)?fa:x);
        }
    }
}
void Access(int x)
{
    for(int y=0;x;y=x,x=t[x].f)
    {
        splay(x);
        rson=y;
        pushup(x);
    }
}
void dfs(int u)
{
    dep[u]=dep[t[u].f]+1;
    t[u].val1=(qpow(dep[u],K)-qpow(dep[u]-1,K)+mod)%mod;
    for(int i=hd[u];i;i=nex[i])    dfs(to[i]);
    pushup(u);
}
int main()
{
    // setIO("input");
    int i,j;
    scanf("%d%d%d",&n,&Q,&K);
    for(i=2;i<=n;++i)
    {
        scanf("%d",&t[i].f),add(t[i].f,i);
    }
    dep[1]=1,dfs(1);
    for(i=1;i<=Q;++i)
    {
        int x,y;
        scanf("%d%d",&x,&y);
        a[x].push_back(sol(y,i));
    }
    for(i=1;i<=n;++i)
    {
        Access(i),splay(i),mark(i,1);
        for(j=0;j<a[i].size();++j)
        {
            Access(a[i][j].y),splay(a[i][j].y);
            answer[a[i][j].id]=t[a[i][j].y].sum2%mod;
        }
    }
    for(i=1;i<=Q;++i)    printf("%d\n",answer[i]);
    return 0;
}