二叉树的序列化

题目：
请实现两个函数，分别用来序列化和反序列化二叉树

思路：
运用前序遍历的思路进行序列化,如果遇到null用#符号代替

代码:

/**
 * Created by Hammy on 2018/2/1.
 */
public class SerializeAndDeSerialize
{
    private int index = -1;
    
    public String Serialize(TreeNode root){
        StringBuffer stringBuffer = new StringBuffer();
        if(root == null){
            stringBuffer.append("#,");
            return stringBuffer.toString();
        }
        stringBuffer.append(root.val + ",");
        stringBuffer.append(Serialize(root.left));
        stringBuffer.append(Serialize(root.right));
        
        return stringBuffer.toString();
    }
    
    public TreeNode Deserialize(String str){
        index++;
        int length = str.length();
        if(index >= length){
            return null;
        }
        String[] strings = str.split(",");
        TreeNode treeNode = null;
        if(!strings[index].equals("#")){
            treeNode = new TreeNode(Integer.valueOf(strings[index]));
            treeNode.left = Deserialize(str);
            treeNode.right = Deserialize(str);
        }
        return treeNode;
    }
    
}