Q1 PepCoding | Number Of Employees Under Every Manager

import java.io.*;
import java.util.*;

public class Main {

  public static void findcount(HashMap<String , String> map){
    
//make a hashmap to store tree information and store root as ceo 

    HashMap<String , HashSet<String>> tree = new HashMap<>();
    String ceo = "";
    
//traverse the map and fill the tree
    
    for(String emp: map.keySet()){  //emp = employee , man = manager
        String man = map.get(emp);
        
        if(man.equals(emp)) ceo = man;
        
        else{
            
            //if manager already exists
            if(tree.containsKey(man)){
                tree.get(man).add(emp);
            }
            else{
                HashSet<String> emps = new HashSet<>();
                emps.add(emp);
                tree.put(man,emps);
             }
        }
        
    }

// make a result Hashmap to store employee:employees under them
//write getsize() recurisive tree function to find employees under manager and pass ceo as root
    
    HashMap<String, Integer> result = new HashMap<>();
    getsize(tree , ceo , result);

    for(String emp : result.keySet())
        System.out.println(emp + " " + result.get(emp));
    

  }
  
 //this is a normal getsize recursive functions in general trees
 
  public static int getsize(HashMap<String , HashSet<String>> tree,
  String man , HashMap<String, Integer> result){
    
//if it doesn't exist in the tree its a leaf node with 0 under employees

    if(tree.containsKey(man) == false){
        result.put(man,0);
        return 1;
    }
    
    int size = 0;
    
    //traversing the tree
    
    for(String emp : tree.get(man)){
        
        int cs = getsize(tree,emp,result);
        size += cs;
    }
    
    result.put(man,size);   //putting size infront of that employee
    return size+1;      //return size and +1 including that employee
  }
  
  public static void main(String[] args){
    Scanner scn = new Scanner(System.in);
    int n = scn.nextInt();
    
    HashMap<String , String>map = new HashMap<String , String>();
    
    for(int i=0 ; i < n ; i++)
    map.put(scn.next(),scn.next());
    
    findcount(map);
  }

}