Custom Tree Problem

// C# program to create a custom tree 
// from a given set of links.
using System;

// The main class that represents tree 
// and has main method
class Tree
{
    public TreeNode root;
    
    /* Returns an array of trees from links input.  
    Links are assumed to be Strings of the form 
    "<s> <e>" where <s> and <e> are starting and 
    ending points for the link. The returned array is
    of size 26 and has non-null values at indexes 
    corresponding to roots of trees in output */
    public Tree[] buildFromLinks(String [] links) 
    {
            
        // Create two arrays for nodes and forest
        TreeNode[] nodes = new TreeNode[26]; 
        Tree[] forest = new Tree[26];         
    
        // Process each link 
        foreach (String link in links) 
        {
            char []sep = {' ',' '};
            
            // Find the two ends of current link
            String[] ends = link.Split(sep);
            int start = (int) (ends[0][0] - 'a'); // Start node
            int end = (int) (ends[1][0] - 'a'); // End node             
                        
            // If start of link not seen before, 
            // add it two both arrays
            if (nodes[start] == null) 
            {             
                nodes[start] = new TreeNode((char) (start + 'a')); 
                
                // Note that it may be removed later when 
                // this character is last character of a link. 
                // For example, let we first see a--->b, 
                // then c--->a. We first add 'a' to array 
                // of trees and when we see link c--->a,
                // we remove it from trees array.
                forest[start] = new Tree(nodes[start]);                                         
            } 
            
            // If end of link is not seen before, 
            // add it to the nodes array
            if (nodes[end] == null)                             
                nodes[end] = new TreeNode((char) (end + 'a'));                                 
            
            // If end of link is seen before, 
            // remove it from forest if it exists there.
            else forest[end] = null; 

            // Establish Parent-Child Relationship
            // between Start and End
            nodes[start].addChild(nodes[end], end);
        }     
        return forest;
    }
    
    // Constructor 
    public Tree(TreeNode root) { this.root = root; } 
    
    public static void printForest(String[] links)
    {
        Tree t = new Tree(new TreeNode('\0'));
        foreach (Tree t1 in t.buildFromLinks(links)) 
        {
            if (t1 != null) 
            { 
                t1.root.printTreeIdented("");
                Console.WriteLine("");
            } 
        }
    }     
    
    // Driver Code
    public static void Main(String[] args) {
        String [] links1 = {"a b", "b c", "b d", "a e"};
        Console.WriteLine("------------ Forest 1 ----------------");
        printForest(links1);     
        
        String [] links2 = {"a b", "a g", "b c", "c d", "d e",
                            "c f", "z y", "y x", "x w"};
        Console.WriteLine("------------ Forest 2 ----------------");
        printForest(links2);     
    }
}

// Class to represent a tree node
public class TreeNode 
{ 
    TreeNode []children;
    char c;
    
    // Adds a child 'n' to this node
    public void addChild(TreeNode n, int index) 
    { 
        this.children[index] = n;
    } 
    
    // Constructor
    public TreeNode(char c)
    { 
        this.c = c; this.children = new TreeNode[26];
    }
    
    // Recursive method to print indented tree
    // rooted with this node.
    public void printTreeIdented(String indent) 
    {     
        Console.WriteLine(indent + "-->" + c);
        foreach (TreeNode child in children)
        {
            if (child != null) 
                child.printTreeIdented(indent + " |");
        }     
    } 
}

// This code is contributed by Rajput-Ji