606. Construct String from Binary Tree

606. Construct String from Binary Tree

好久不刷题，简单题都不会了=_=，看来刷题不能停。

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution(object):
    def tree2str(self, t):
        """
        :type t: TreeNode
        :rtype: str
        """
        if t == None:
            return ''
        if t.left == None and t.right == None:
            return str(t.val)
        elif t.left and t.right:
            return str(t.val) + '(' + self.tree2str(t.left) + ')' + '(' + self.tree2str(t.right) + ')'
        elif t.left:
            return str(t.val) + '(' + self.tree2str(t.left) + ')'
        else:
            return str(t.val) + '()' + '(' + self.tree2str(t.right) + ')'