Blood Cousins Return DSU on tree

#include<bits/stdc++.h>
using namespace std;
const int N = 2e6 + 10;
int n, m, Maxdep;
map<string, int> name;
vector<int> mp[N];
vector<pair<int, int>> qus[N];
int ans[N];
int col[N];

int dfn[N], cnt, ct, fa[N];//cnt是dfn序， ct是颜色种类
int L[N], R[N];
int dep[N],sz[N],dg[N];
void dfs(int x, int Dep) {
    L[x] = ++cnt;
    dfn[cnt] = x;
    dep[x] = Dep;
    Maxdep = max(Maxdep, dep[x]);
    sz[x] = 1;
    int maxn = 0;
    for (auto y : mp[x]) {
        if (y == fa[x]) continue;
        dfs(y, Dep + 1);
        sz[x] += sz[y];
        if (sz[y] > maxn) {
            maxn = sz[y];
            dg[x] = y;//重儿子
        }
    }
    R[x] = cnt;
}
set<int> cntt[N];
void dfs1(int x, int fa, bool kep) {
    for (auto y : mp[x]) {
        if (y != fa && y != dg[x]) dfs1(y, x, false);
    }//先做自己的所有轻儿子

    if (dg[x]) dfs1(dg[x], x, true);//做重儿子并保留

    for (auto y : mp[x])
        if (y != fa && y != dg[x])
            for (int i = L[y]; i <= R[y]; i++)
                cntt[dep[dfn[i]]].insert(col[dfn[i]]);

    cntt[dep[x]].insert(col[x]);

    for (auto y : qus[x]) {
        ans[y.second] = cntt[y.first + dep[x]].size();
    }

    if (kep == false)
        for (int i = 1; i <= Maxdep; i++)
            cntt[i].clear();
            
}
int main() {
    cin >> n;
    for (int i = 1; i <= n; i++) {
        string s;
        cin >> s >> fa[i];
        if (!name[s]) name[s] = ++ct;//名字没出现过，那么就是一种新颜色
        col[i] = name[s];//每个人对应一个颜色（名字）
        if(fa) mp[i].push_back(fa[i]);
        if(fa) mp[fa[i]].push_back(i);
    }
    
    for (int i = 1; i <= n; i++)
        if (!fa[i]) dfs(i, 1);
    cin >> m;
    for (int i = 1; i <= m; i++) {
        int a, b; cin >> a >> b;
        qus[a].push_back({ b,i });
    }

    for (int i = 1; i <= n; i++)
        if (!fa[i]) dfs1(i, 0, false);

    for (int i = 1; i <= m; i++)
        cout << ans[i] << endl;
}