题目

#include <bits/stdc++.h>
using namespace std;
#define int long long
#define pb push_back
#define fi first
#define se second
#define lson p << 1
#define rson p << 1 | 1
#define ll long long
const int maxn = 1e6 + 5, inf = 1e9, maxm = 4e4 + 5, base = 37;
const int N = 4e3;
const int mod = 1e9 + 7;
// const int mod = 998244353;
// const __int128 mod = 212370440130137957LL;int n, m;
int a[maxn];//long long ? maxn ? n? m?
void solve(){ll res = 0;cin >> n;vector<vector<int>> G(n + 1);vector<int> siz(n + 1), sum(n + 1);for(int i = 1; i <= n; i++){cin >> a[i];}for(int i = 2; i <= n; i++){int j;cin >> j;G[j].pb(i);}auto init = [&](auto self, int u) -> void {siz[u] = 1;sum[u] = a[u];for(auto v : G[u]){self(self, v);siz[u] += siz[v];sum[u] += sum[v];}};init(init, 1);res = 0;int tot = 0;auto dfs = [&](auto self, int u) -> void {vector<int> vec;int dfn = ++tot;res += dfn * a[u];for(auto v : G[u]){vec.pb(v);}sort(vec.begin(), vec.end(), [&](int i, int j){return siz[i] * sum[j] > siz[j] * sum[i];//按siz / sum降序排序});for(auto v : vec){self(self, v);}};dfs(dfs, 1);cout << res << '\n';
}signed main(){ios::sync_with_stdio(0);cin.tie(0);cout << fixed << setprecision(9);int T = 1;// cin >> T;while (T--){solve();}return 0;
}