Codeforces 115A

思路：求树的高度。用并查集，不要压缩路径。

#include<iostream>
#include<cstdio>
#include<cstring>
using namespace std;
int father[2005], cnt;
int max(int x, int y)
{
    return x > y ? x : y;
}
void init(int n)
{
    for(int i = 1;i <= n;i ++)
        father[i] = i;
}

void find(int x)
{
    if(x == father[x])
        return;
    cnt ++;
    find(father[x]);
}

void unit(int x, int y)
{
    father[x] = y;
    return ;
}

int main(int argc, char const *argv[]) 
{
    int n, ans, temp;
    while(~scanf("%d", &n))
    {
        init(n);
        for(int i = 1;i <= n;i ++)
        {
            scanf("%d", &temp);
            if(temp != -1)
                unit(i, temp);
        }
        ans = 0;
        for(int i = 1;i <= n;i ++)
        {
            cnt = 0;
            find(i);
            ans = max(ans, cnt);
        }
        printf("%d\n", ans+1);
    }
    return 0;
}