传送门

发现其实就是左右2棵子树，左儿子选到某个值的概率就是
选最大值的概率∗右儿子的值比它小的概率选最大值的概率*右儿子的值比它小的概率选最大值的概率∗右儿子的值比它小的概率
+选最小值的概率∗右儿子的值比他大的概率+选最小值的概率*右儿子的值比他大的概率+选最小值的概率∗右儿子的值比他大的概率

右儿子类似

由于保证所有值不都相等
然后上线段树合并mergemergemerge的时候dpdpdp一下就完了

复杂度O(nlogn)O(nlogn)O(nlogn)

#include<bits/stdc++.h>
using namespace std;
const int RLEN=1<<20|1;
inline char gc(){static char ibuf[RLEN],*ib,*ob;(ib==ob)&&(ob=(ib=ibuf)+fread(ibuf,1,RLEN,stdin));return (ib==ob)?EOF:*ib++;
}
inline int read(){char ch=gc();int res=0,f=1;while(!isdigit(ch))f^=ch=='-',ch=gc();while(isdigit(ch))res=(res+(res<<2)<<1)+(ch^48),ch=gc();return f?res:-res;
}
const int mod=998244353;
const int N=500005;
inline int add(int a,int b){return a+b>=mod?a+b-mod:a+b;
}
inline void selfadd(int &a,int b){a=add(a,b);
}
inline int dec(int a,int b){return a>=b?a-b:a-b+mod;
}
inline int mul(int a,int b){return 1ll*a*b>=mod?1ll*a*b%mod:a*b;
}
inline void selfmul(int &a,int b){a=mul(a,b);
}
inline int ksm(int a,int b,int res=1){for(;b;b>>=1,a=mul(a,a))if(b&1)selfmul(res,a);return res;
}
int cnt[N],son[N][2],rt[N],val[N],pmx[N];
int fa[N],ori[N],ans,n;
struct node{int k,p;friend inline bool operator <(const node &a,const node &b){return a.k<b.k;}
}q[N];int tot;
namespace Seg{#define mid ((l+r)>>1)int tot,cnt,mxa,mxb;int lc[N*22],rc[N*22],tag[N*22],tr[N*22];void update(int &u,int l,int r,int k){u=++tot,tag[u]=1,tr[u]=1;if(l==r)return;if(k<=mid)update(lc[u],l,mid,k);else update(rc[u],mid+1,r,k);}inline void pushup(int u){tr[u]=add(tr[lc[u]],tr[rc[u]]);}inline void pushnow(int u,int t){selfmul(tag[u],t);selfmul(tr[u],t);}inline void pushdown(int u){if(tag[u]==1)return;int &t=tag[u];if(lc[u])pushnow(lc[u],t);if(rc[u])pushnow(rc[u],t);t=1;}int merge(int r1,int r2,int g){if(!r1&&!r2)return 0;pushdown(r1),pushdown(r2);if(!r1){selfadd(mxb,tr[r2]);pushnow(r2,dec(add(mxa,g),mul(2,mul(mxa,g))));return r2;}if(!r2){selfadd(mxa,tr[r1]);pushnow(r1,dec(add(mxb,g),mul(2,mul(mxb,g))));;return r1;}rc[r1]=merge(rc[r1],rc[r2],g);lc[r1]=merge(lc[r1],lc[r2],g);pushup(r1);return r1;}void dfs(int u){if(!::cnt[u])return;else if(::cnt[u]==1)dfs(son[u][0]),rt[u]=rt[son[u][0]];else if(::cnt[u]==2){dfs(son[u][0]),dfs(son[u][1]);mxa=mxb=0;rt[u]=merge(rt[son[u][0]],rt[son[u][1]],pmx[u]);}}void calc(int u,int l,int r){if(!tr[u])return;pushdown(u);if(l==r){cnt++;selfadd(ans,mul(mul(mul(cnt,ori[l]),tr[u]),tr[u]));return;}calc(lc[u],l,mid),calc(rc[u],mid+1,r);}
}
signed main(){n=read();for(int i=1;i<=n;i++){fa[i]=read();son[fa[i]][cnt[fa[i]]++]=i;}int inv=ksm(10000,mod-2);for(int i=1;i<=n;i++){int k=read();if(cnt[i])pmx[i]=mul(k,inv);else{q[++tot]=(node){k,i};}}sort(q+1,q+tot+1);for(int i=1;i<=tot;i++){ori[i]=q[i].k,Seg::update(rt[q[i].p],1,tot,i);}Seg::dfs(1);Seg::calc(rt[1],1,tot);cout<<ans;
}