在Java中将层次结构列表转换为平面列表 [英] Convert hierarchical list to a flat list in java

问题描述

我有一个如下所示的分层list，我想将其转换为平面list.

I have a hierarchical list like below and I want to convert it to a flat list.

我写了一个叫做convertToFlatList的方法并使用了它.但是最终结果中缺少一些要素.我做错了什么?

I have wrote a method called convertToFlatList and have used it. But some elements are missing in the final results. What did i do wrong?

还有比我以前将列表转换为平面列表更好的方法吗?

Also is there a better way than the way I have used to convert my list to a flat list?

我添加了示例代码和类似于我在场景中必须使用的对象的东西.最终结果应为1、2、3、4、5、6、7

I have added a sample code and something similar to the Objects I have to used in my scenario. Final result should be 1, 2, 3, 4, 5, 6, 7

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class Main
{
  public static void main(String[] args)
  {
    Member memberOne = new Member(1);
    Member memberTwo = new Member(2);
    Member memberThree = new Member(3);
    Member memberFour = new Member(4);
    Member memberFive = new Member(5);
    Member memberSix = new Member(6);
    Member memberSeven = new Member(7);

    memberTwo.setChildren(Arrays.asList(memberThree, memberFour));
    memberFour.setChildren(Arrays.asList(memberFive, memberSix));

    List<Member> memberList = Arrays.asList(memberOne, memberTwo, memberSeven);
    List<Member> flatList = new ArrayList<>();
    List<Member> convertedList = convertToFlatList(memberList, flatList);
    System.out.println(convertedList);
  }

  private static List<Member> convertToFlatList(List<Member> memberList, List<Member> flatList)
  {
    for (Member member : memberList)
    {
      if (member.getChildren() != null)
      {
        convertToFlatList(member.getChildren(), flatList);
      }
      else
      {
        flatList.add(member);
      }
    }
    return flatList;
  }
}

class Member
{
  private List<Member> children;

  private int memberId;

  Member(int memberId)
  {
    this.memberId = memberId;
  }

  List<Member> getChildren()
  {
    return children;
  }

  void setChildren(List<Member> children)
  {
    this.children = children;
  }

  int getMemberId()
  {
    return memberId;
  }

  void setMemberId(int memberId)
  {
    this.memberId = memberId;
  }

  @Override
  public String toString()
  {
    return String.valueOf(this.memberId);
  }
}

推荐答案

如果Member有子代，则可以将子代正确地添加到扁平化列表中，但是会错过Member本身.只需将成员的添加移动到else块的外部即可，添加应该没问题:

If a Member has children, you correctly add the children to the flattened list, but miss the Member itself. Just move the addition of the member outside of the else block add you should be fine:

private static List<Member> 
convertToFlatList(List<Member> memberList, List<Member> flatList)
{
    for (Member member : memberList)
    {
        // Always add the member to flatList
        flatList.add(memeber);

        // If it has children, add them toore
        if (member.getChildren() != null)
        {
            convertToFlatList(member.getChildren(), flatList);
        }
    }
    return flatList;
}

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