Leetcode 297. Serialize and Deserialize Binary Tree, Java

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//'main' method must be in a class 'Rextester'.
//Compiler version 1.8.0_111

//Leetcode 297. Serialize and Deserialize Binary Tree
import java.util.*;
import java.lang.*;

class Node{
    int val;
    Node left;
    Node right;
    Node(int v){
        val=v;
    }
}

class Rextester
{  
    public static void main(String args[])
    {
        System.out.println("Hello, World!");

/*Node n = new Node(1);
        n.left = new Node(2);
        n.right = new Node(3);
        n.left.left=null;
        n.left.right=null;
        n.right.left = new Node(4);
        n.right.right = new Node(5);
        n.right.left.left = null;
        n.right.left.right = null;
        n.right.right.left = null;
        n.right.right.right = null;

System.out.println(serialize(n));*/

Node root = deSerialize("1,2,null,null,3,4,null,null,5,null,null,");

}

public static String serialize(Node root) {
        return recSerialize(root,"");
    }
    
    public static String recSerialize(Node n,String str){
        if(n==null){
            str+="null,";
            return str;
        }

str+=n.val+",";
        str=recSerialize(n.left,str);
        str=recSerialize(n.right,str);
        return str;
    }

public static Node deSerialize(String str){
        String[] tokens = str.split(",");
        List<String> lst = new ArrayList<String>(Arrays.asList(tokens));
        return recDeSerialize(lst);
    }

public static Node recDeSerialize(List<String> lst){
        if(lst.get(0).equals("null")){
            lst.remove(0);
            return null;
        }
        Node newNode = new Node(Integer.valueOf(lst.get(0)));
        lst.remove(0);
        newNode.left = recDeSerialize(lst);
        newNode.right = recDeSerialize(lst);

return newNode;
            
    }

}

[ + ] Show input
Compilation time: 0.73 sec, absolute running time: 0.16 sec, cpu time: 0.13 sec, memory peak: 18 Mb, absolute service time: 0,9 sec