序列化二叉树

序列化：前序遍历二叉树存入字符串中；反序列化：根据前序遍历重建二叉树

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