C :

#include<stdio.h>

#include<stdlib.h>

typedef struct node

{

    int data;

    struct node *next;

}Link;


void insertNode(Link *head, int data) {

    Link *p = head;

    Link *q = (Link *)malloc(sizeof(Link));

    q->data = data;

    q->next = NULL;

    while(p->next != NULL) p=p->next;

    p->next = q;

}

void freeNode(Link *head) {

    Link *p = head->next;

    Link *q;

    head->next = NULL;

    while(p != NULL){

        q = p;

        p=p->next;

        free(q);

    }

}

 

int deep(Link ** tree, int start) {

    int depth = 1;

    Link *p;

    if(tree[start]->next == NULL) {

        return depth;

    }

    p= tree[start]->next;

    while(p!= NULL){

        int tmp = deep(tree, p->data - 1);

        if(tmp > depth) depth = tmp;

        p=p->next;

    }

 

    return depth + 1;

}

 

int main(){

    int count, i,j;

    int a, b;

    Link **tree;

     

    scanf("%d", &count);j=count-1;

    tree = (Link **)malloc(sizeof(Link*)*count);

    for(i=0;i<count;++i) {

        tree[i] = (Link *)malloc(sizeof(Link));

        tree[i]->next = NULL;

    }

    while(j>0){
scanf("%d%d",&a, &b);
        if(a>0 && b>0) {

            insertNode(tree[a-1], b);
j--;
        }

    }

    printf("%d\n", deep(tree, 0));

    for(i=0;i<count;++i) {

        freeNode(tree[i]);

        free(tree[i]);

    }

    free(tree);

    return 0;

}

C++ :

#include <iostream>
using namespace std;
int main()
{ int a[10000],i,n,z,x,m;
 cin>>n;  a[1]=1;
    while (cin>>z>>x)
      a[x]=a[z]+1;
     m=1;
    for (i=1;i<=n;++i)
     if (a[i]>m) m=a[i];
    cout<<m;
return 0;    
}

Pascal :

program p2450;
var a:array[1..100,1..100] of longint;
    n,i,j,k,x,y,max:longint;
begin
  readln(n);
  for i:=1 to n do
   for j:=1 to n do
     a[i,j]:=maxint;
  for i:=1 to n-1 do
  begin
    readln(x,y);
	a[x,y]:=1;
	a[y,x]:=1;
  end;
  for k:=1 to n do
   for i:=1 to n do
    for j:=1 to n do
     if (i<>k) and (j<>k) and (i<>j) then
       if a[i,k]+a[k,j]<a[i,j] then
        a[i,j]:=a[i,k]+a[k,j];
  max:=0;		
  for i:=2 to n do
    if a[1,i]>max then max:=a[1,i];
  writeln(max+1);
end.

Java :

import java.util.Scanner;
import java.util.ArrayList;
/**
 *
 * @author zhenghan33
 */
public class Main {

    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        Scanner cin=new Scanner(System.in);
        int number=cin.nextInt();
        ArrayList<Node> a=new ArrayList<>();
        a.add(new Node(1,1));
        while(cin.hasNext())
        {
            int m=cin.nextInt();
            int n=cin.nextInt();
            int height=1;
            for(int i=0;i<a.size();++i)
                if(a.get(i).getId()==m)
                {
                    height=a.get(i).getHeight()+1;
                    break;
                }
            a.add(new Node(n,height));
        }
        int max=1;
        for(int i=0;i<a.size();++i)
        {
            if(a.get(i).getHeight()>max)
                max=a.get(i).getHeight();
        }
        System.out.println(max);
    }

}
class Node{
    private int id;
    private int height;
    Node(int a,int b)
    {
        id=a;
        height=b;
    }
    public int getId(){return id;}
    public int getHeight(){return height;}
    public void setId(int n){id=n;}
    public void setHeight(int n){height=n;}
}