/*
// Definition for a Node.
public class Node {
    public int val;
    public IList<Node> children;

    public Node() {}

    public Node(int _val) {
        val = _val;
    }

    public Node(int _val, IList<Node> _children) {
        val = _val;
        children = _children;
    }
}
*/

public class WrappableInt {
    private int val;
    public WrappableInt(int x) {
        val = x;
    }
    public int getValue() {
        return val;
    }
    public void increment() {
        val++;
    }
}

public class Codec {
    
    // Encodes a tree to a single string.
    public string serialize(Node root) {
        StringBuilder sb = new StringBuilder();
        serializeHelper(root, sb);
        return sb.ToString();
    }
    
    public void serializeHelper(Node node, StringBuilder sb) {
        if(node == null) {
            return;
        } 
        sb.Append(node.val);
        sb.Append(node.children.Count);
        foreach(Node child in node.children) {
            serializeHelper(child, sb);
        }
    }
	
    // Decodes your encoded data to tree.
    public Node deserialize(string data) { 
        Console.WriteLine(data);
        if(String.IsNullOrEmpty(data)) {
            return null;
        }
        
        return deserializeHelper(data, new WrappableInt(0));
    }   
    
    public Node deserializeHelper(string data, WrappableInt index) {
        if(index.getValue() >= data.Length) {
            return null;
        }
        Node node = new Node(data[index.getValue()], new List<Node>());
        index.increment();
        var num = data[index.getValue()];   
        for(int i = 0; i < num; ++i) {
            index.increment();
            node.children.Add(deserializeHelper(data, index));
        }
        return node;
    }
}

// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.deserialize(codec.serialize(root));

System.NullReferenceException: Object reference not set to an instance of an object.
Line 72: Serialize.serialize (Node root) in __Driver__.cs
Line 107: __Driver__.Main (System.String[] args) in __Driver__.cs
[ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object.
Line 72: Serialize.serialize (Node root) in __Driver__.cs
Line 107: __Driver__.Main (System.String[] args) in __Driver__.cs