CF1739D

回头膜一下jls的

#include <bits/stdc++.h>
/*
#include<ext/pb_ds/assoc_container.hpp>
#include<ext/pb_ds/hash_policy.hpp>
*/
using namespace std;

const double eps = 1e-10;
const double pi = 3.1415926535897932384626433832795;
const double eln = 2.718281828459045235360287471352;

#define f(i, a, b) for (int i = a; i <= b; i++)
#define scan(x) scanf("%d", &x)
#define mp make_pair
#define pb push_back
#define lowbit(x) (x&(-x))

#define fi first
#define se second
#define SZ(x) int((x).size())
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define summ(a) (accumulate(all(a), 0ll))

typedef unsigned long long ull;
typedef pair<int,int> pii;
typedef vector<int> vi;

using ll=long long;

ll tt,n,k,fa[(int)2e5+9],cnt; 
vi g[(int)2e5+9];

ll dfs(int u,int fa,int dep,ll x){
    ll res=0;
    for(auto it:g[u]){
        res=max(dfs(it,u,dep+1,x),res);
    }
    res+=1;
    if(res>=x&&fa!=1)cnt+=1,res=0;
    //cerr<<u<<"::"<<res<<"__"<<x<<"??"<<cnt<<"\n";
    return res;
}

bool check(ll x){
    cnt=0;
    dfs(1,1,0,x);
    //cerr<<"++"<<cnt<<"__\n";
    return cnt<=k;
}

void solve(){
    cin>>n>>k;
    for(int i=1;i<=n;++i)g[i].clear();
    for(int i=2;i<=n;++i)cin>>fa[i],g[fa[i]].push_back(i);
    ll l=1,r=n-1;
    while(l<r){
        ll mid=(l+r)>>1;
        if(check(mid))r=mid;
        else l=mid+1;
    }
    cout<<l<<'\n';
}

int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);
    cin>>tt;
    f(sb,1,tt)solve();
    return 0;
}