第三题 大佬可以帮忙看看哪里错了么？只过了百分之20 self.ans = 0         def traverse(self,root):             if root == None:                 return 0             left = self.traverse(self, root.left)             right = self.traverse(self, root.right)             if left == right:                 self.ans += 1             else:                 self.ans =2* max(left,right)             return left + right + 1         return self.ans