河南省2022ccpc J-Mex Tree

// mex 必须把权值为0的点设置为根节点，经过测试发现根节点不同维护出的siz数组也会不同
#include <bits/stdc++.h>
using namespace std;
const int N = 1e6 + 10, M = 2 * N;
int h[N], e[M], ne[M], w[M], idx;
int id[N], siz[N], mn[N]; // id[w]表示权值为w对应的节点编号,siz[i] 表示i号点的子树大小 mn[i]记录i号点子树中的最小权值
int n;
void add(int a, int b)
{
    e[idx] = b, ne[idx] = h[a], h[a] = idx++;
}
void dfs(int u, int f)
{
    siz[u] = 1, mn[u] = w[u];
    for (int i = h[u]; ~i; i = ne[i])
    {
        int j = e[i];
        if (j == f)
            continue;
        dfs(j, u);
        siz[u] += siz[j];
        if (mn[u] > mn[j])
            mn[u] = mn[j];
    }
    return;
}
int main()
{
    memset(h, -1, sizeof h);
    scanf("%d", &n);
    for (int i = 1; i <= n; i++)
    {
        scanf("%d", &w[i]);
        id[w[i]] = i;
    }
    for (int i = 2; i <= n; i++)
    {
        int x;
        scanf("%d", &x);
        add(x, i), add(i, x);
    }
    dfs(id[0], -1);
    int mx = 0;
    for (int i = h[id[0]]; ~i; i = ne[i])
    {
        int j = e[i];
        if (siz[j] > mx)
            mx = siz[j];
    }
    printf("%d ", mx);
    for (int k = 1; k <= n - 1; k++)
    {
        if (mn[id[k]] >= k)
            printf("%d ", n - siz[id[k]]);
        else
            printf("0 ");
    }
    printf("%d\n", n);
    return 0;
}