京东笔试题Java后端

import java.util.*;
 public class JDQ1 {
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();    
        List<int[]>edges=new ArrayList<int[]>();
        for(int i=0;i<n-1;i++) {
            int[]temp=new int[2];
            temp[0]=sc.nextInt();
            temp[1]=sc.nextInt();
            edges.add(temp);
            
        }
        System.out.print(new JDQ1().getMinTime(n, edges));
    }
    public int getMinTime(int n,List<int[]>edges) {
        JDQ1TreeNode root=generate(n,edges);
        List<Integer>list=new ArrayList<Integer>();
        for(JDQ1TreeNode temp:root.children)
        list.add(new JDQ1TreeNode().getNumberOfNodes(temp));
        return Collections.max(list);
    }
    
    public JDQ1TreeNode generate(int n,List<int[]>edges) {
        JDQ1TreeNode[]nodes=new JDQ1TreeNode[n];
        for(int i=0;i<n;i++)nodes[i]=new JDQ1TreeNode(i,null);
        nodes[0].children=new HashSet<JDQ1TreeNode>();
        while(!edges.isEmpty())
        for(int i=0;i<edges.size();i++) {
            //System.out.println(edges.size());
            int[]temp=edges.get(i);
            int begin=temp[0]-1,end=temp[1]-1;
            if(nodes[begin].children!=null) {
                nodes[begin].children.add(nodes[end]);
                if(nodes[end].children==null)nodes[end].children=new HashSet<JDQ1TreeNode>();
                edges.remove(i);
            }
            
            else if(nodes[end].children!=null) {
                nodes[end].children.add(nodes[begin]);
                if(nodes[begin].children==null)nodes[begin].children=new HashSet<JDQ1TreeNode>();
                edges.remove(i);
        }
        }
        return nodes[0];
        
    }
 }
 class JDQ1TreeNode{
    int id;
    HashSet<JDQ1TreeNode> children;
    public JDQ1TreeNode(int id,HashSet<JDQ1TreeNode> children) {
        super();
        this.id = id;
        this.children = children;
    }
    public JDQ1TreeNode() {}
    
    public int getHeight(JDQ1TreeNode root) {
        if(root.children==null)return 1;
        List<Integer>list=new ArrayList<Integer>();
        for(JDQ1TreeNode temp:root.children)
            list.add(getHeight(temp));
        return Collections.max(list)+1;
    }
    public int getNumberOfNodes(JDQ1TreeNode root) {
        if(root.children==null)return 1;
        
        int sum=0;
        for(JDQ1TreeNode temp:root.children)
            sum+=(getNumberOfNodes(temp));
        return sum+1;
    }
 }