[leetCode刷题笔记]606. Construct String from Binary Tree

奇葩的规则，左子树的规则必须打。

/** * Definition for a binary tree node. * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public String tree2str(TreeNode t) {        if (t == null) return "";        StringBuilder sb = new StringBuilder();        sb.append(t.val);                if (t.left != null || t.right != null) {            sb.append("(");            sb.append(tree2str(t.left));            sb.append(")");        }         if (t.right != null) {            sb.append("(");            sb.append(tree2str(t.right));            sb.append(")");        }                return sb.toString();                            }}