C++ 代码

#include <iostream>
#include <cstring>

using namespace std;

const int N  = 1e5 + 10;

int h[N], ne[N], e[N], idx;

void add(int a, int b)
{
    e[idx] = b;
    ne[idx] = h[a];
    h[a] = idx++;
}

int find(int x)
{
    int cnt = 0, m = -1;
    for(int i = h[x]; i != -1; i = ne[i])
    {
        cnt++;
        int k = e[i];
        m = max(m, find(k));  
    }

    if(cnt == 0) return 1;
    return m + cnt;   
}

int main()
{
    int n ;
    cin >> n;

    memset(h, -1, sizeof h);

    for(int i = 2;  i <= n; i++)
    {
        int x;
        cin >> x;
        add(x, i);
    }

    cout << find(1) - 1;

    return 0;
}