#include<bits/stdc++.h>
using namespace std;
const int N=5e4+10,W=6e4+10;
vector<int>dp[N];
int n,m,siz[N],rdfn[N],len,w[N],v[N],d[N];vector<int>G[N];
void dfs(int x,int f)
{
//	printf("%d %d\n",x,f);
	siz[x]=1;
	for(int y:G[x])if(y!=f)
	{
		dfs(y,x);
		siz[x]+=siz[y];
	}
	rdfn[++len]=x;
}
int main()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		cin>>d[i];
		G[d[i]].push_back(i);
	}
	for(int i=1;i<=n;i++)cin>>w[i];
	for(int i=1;i<=n;i++)cin>>v[i];
	for(int i=0;i<=n+2;i++)dp[i].resize(m+2);
	dfs(0,0);
	for(int i=1;i<=len;++i)
	{
        int x=rdfn[i];
//        printf("%d %d\n",i,x);
		for(int j=0;j<=m;++j)
		{
            dp[i][j]=dp[i-siz[x]][j];
            if(j>=w[x])dp[i][j]=max(dp[i][j],dp[i-1][j-w[x]]+v[x]);
        }
    } 
//    cout<<6;return 0;
    int ans=0;
    for(int i=1;i<=m;i++)ans=max(ans,dp[n][i]);
    cout<<ans;
    return 0;
}

decltype版本：

#include <bits/stdc++.h>
using namespace std;
const int T=6.06e7+10,N=5e4+10;
int n,W,ff[T],w[N],v[N],s[N],ww[N],vv[N],ss[N],id;
vector<int>G[N]; 
void dfs(int x,int fa)
{
    s[x]=1;
    for(int y:G[x])if(y!=fa)   
    {
       dfs(y,x);
       s[x]+=s[y];
    }
    ++id;
    ww[id]=w[x];
    vv[id]=v[x];
    ss[id]=s[x];
}
signed main()
{
    scanf("%d%d",&n,&W);
    int (&f)[n+2][W+1]=decltype(f)(ff);
    for(int i=1,y;i<=n;++i)
    {
        scanf("%d",&y);
        G[i].push_back(y);
        G[y].push_back(i);
    }
    for(int i=1;i<=n;++i)scanf("%d",&w[i]);
    for(int i=1;i<=n;++i)scanf("%d",&v[i]);    
    id=0;dfs(0,0);
    memset(f,0,sizeof(f));
    for(int i=1;i<=id;++i)
    {
        for(int j=0;j<=W;++j)
        {
            f[i][j]=f[i-ss[i]][j];
            if(j>=ww[i])f[i][j]=max(f[i][j],f[i-1][j-ww[i]]+vv[i]);
        }
    }
    printf("%d\n",f[id][W]);
    return 0;
}

版本二：

#include <bits/stdc++.h>
using namespace std;
const int T=6.06e7+10,N=5e4+10;
int n,W,f[T],w[N],v[N],s[N],ww[N],vv[N],ss[N],id;
int gid(int x,int y){ return x*(W+1)+y; }//此处不能写 x*W+y ，每行有效列为0~W
vector<int>G[N]; 
void dfs(int x,int fa)
{
    s[x]=1;
    for(int y:G[x])if(y!=fa)   
    {
       dfs(y,x);
       s[x]+=s[y];
    }
    ++id;
    ww[id]=w[x];
    vv[id]=v[x];
    ss[id]=s[x];
}
signed main()
{
    scanf("%d%d",&n,&W);
    for(int i=1,y;i<=n;++i)
    {
        scanf("%d",&y);
        G[i].push_back(y);
        G[y].push_back(i);
    }
    for(int i=1;i<=n;++i)scanf("%d",&w[i]);
    for(int i=1;i<=n;++i)scanf("%d",&v[i]);    
    id=0;dfs(0,0);
    memset(f,0,sizeof(f));
    for(int i=1;i<=id;++i)
    {
        for(int j=0;j<=W;++j)
        {
            f[gid(i,j)]=f[gid(i-ss[i],j)];
            if(j>=ww[i])f[gid(i,j)]=max(f[gid(i,j)],f[gid(i-1,j-ww[i])]+vv[i]);
        }
    }
    printf("%d\n",f[gid(id,W)]);
    return 0;
}