序列化二叉树

class Solution{       String Serialize(TreeNode root) {        StringBuffer str= new StringBuffer();preSearch(root, str);return str.toString();}//前序遍历void preSearch(TreeNode node,StringBuffer s){ if(node==null){//空则用特殊字符表示s.append(",$");return;}s.append(","+node.val);preSearch(node.left,s);preSearch(node.right,s);}//反序列化int index = -1;TreeNode Deserialize(String str) {str = str.substring(1);String[] array = str.split(",");       int len = array.length;        for(String s : array)       s.replace(',', ' ');       if(len == 1)       return null;              TreeNode root = new TreeNode (Integer.parseInt(array[++index]));//CHAR变为int       root.left =  des(array);       root.right = des(array);       return root;}TreeNode des(String[] str){TreeNode node  = null;if(++index < str.length){String ele = str[index];if(!ele .equals("$") ){node = new TreeNode(Integer.parseInt(ele)); node.left = des(str);node.right = des(str);}}return node;}}