Codeforces-SolutionsA/Codes/1997 D - Maximize the Root/1997D.cpp

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#include <bits/stdc++.h>
using namespace std;
#ifdef ONLINE_JUDGE
#define dbg(...)
#else
#include "Assets/debug.h"
#endif
#define int long long
#define ll long long
#define endl '\n'
#define ff first
#define ss second
#define ins insert
#define pb push_back
#define ppb pop_back
#define sz(x) (int)(x).size()
#define all(x) x.begin(), x.end()
#define rep(i,a,b) for(int i=a; i<b; ++i)
#define rrep(i,a,b) for(int i=a; i>=b; --i)
#define yn(f) f? cout<<"YES\n":cout<<"NO\n"
#define FAST (ios_base::sync_with_stdio(false), cin.tie(nullptr));
ll pow(ll x,ll y,ll m=1e9+7) {ll ans=1;x%=m;while(y){if(y&1)ans=(ans*x)%m;x=(x*x)%m;y>>=1;}return ans;}
void solve()
{
int n;
cin>>n;
vector<int>adj[n], v(n);
for(auto &i:v) cin>>i;
rep(i,1,n)
{
int p;
cin>>p;
p--;
adj[p].pb(i);
}
function<int (int node)> dfs = [&](int node)->int
{
int mn = INT_MAX;
for(auto child:adj[node])
mn = min(mn, dfs(child));
dbg(mn);
if(node == 0) return mn+v[0];
if(mn == INT_MAX) return v[node];
if(v[node] >= mn) return mn;
return (mn+v[node])/2;
};
cout<<dfs(0)<<endl;
}
signed main()
{
FAST;
int TCS = 1;
cin >> TCS;
for (int TC = 1; TC <= TCS; ++TC)
{
// cout<<"Case "<<TC<<": ";
solve();
}
}