序列化二叉树

题目描述
请实现两个函数，分别用来序列化和反序列化二叉树

public class Solution {
    
    public int index = -1;
    String Serialize(TreeNode root) {
        
        StringBuffer sb = new StringBuffer();
        if(root == null) {
            
            sb.append("#,");
            return sb.toString();
        }
        sb.append(root.val + ",");
        sb.append(Serialize(root.left));
        sb.append(Serialize(root.right));
        return sb.toString();
    }
    TreeNode Deserialize(String str) {
        
        index ++;
        int len = str.length();
        if(index >= len)
            return null;
        String[] strr = str.split(",");
        TreeNode node = null;
        if(!strr[index].equals("#")) {
            
            node = new TreeNode(Integer.valueOf(strr[index]));
            node.left = Deserialize(str);
            node.right = Deserialize(str);
        }
        return node;
    }
}