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Convert the department list to preorder traversal of the name of department tree

链接：https://www.nowcoder.com/questionTerminal/86dc86da50424b47b25ced3e9f97b056

来源：牛客网

输入

[[“d1”, “d0”, “IT”], [“d2”, “d0”, “RD”], [“d0”, “”, “The Company”], [“d3”, “d0”, “HR”]] 输出 [“The Company”,“HR”,“IT”,“RD”] 说明 On each level of the department tree, departments are listed in alphabetical order of the name

import java.util.*;public class Solution {
       /**     * Convert the department list to preorder traversal of the department tree     * @param departments string字符串二维数组 [["id1", "parentId", "name"]...], there's only one root department with empty parent id.     * @return string字符串一维数组     */    LinkedList
   
     res = new LinkedList<>();    public String[] listToTree (String[][] departments) {
           // write code here        Map
    
      map = new HashMap<>();         int n = departments.length;        Node root=null;        for(int i=0;i
     
       arr1[2].compareTo(arr2[2]));                for(String[] dep: departments) {
               Node parent  = map.get(dep[1]);            if(parent==null) continue;            Node self = map.get(dep[0]);            parent.sons.add(self);        }        dfs(map,root);        return res.toArray(new String[0]);                            }    void dfs(Map
      
        map,Node root) {
           if(root ==null) return;        res.add(root.name);        for(Node child: root.sons) {
               dfs(map,child);        }    }                static class  Node{
           String id;        String parentId;        String name;        List
       
         sons = new LinkedList<>();        Node(String[] x) {
               id = x[0];            parentId = x[1];            name = x[2];        }    }}
       
      
     
    
   

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