101. Symmetric Tree

class Solution:
    def SymCheck(self, ls):
        start = 0
        end = len(ls)-1
        while start < end:
            if ls[start] != ls[end]:
                return False
            start += 1
            end -= 1
        return True

    def isSymmetric(self, root):
        """
        :type root: TreeNode
        :rtype: bool
        """
        if not root:
            return True

        temp = []
        q = collections.deque()
        q.append(root)
        while q:
            num = len(q)
            for i in range(num):
                node = q.popleft()
                if node:
                    temp.append(node.val)
                    if node.left:
                        q.append(node.left)
                    else:
                        q.append(None)

                    if node.right:
                        q.append(node.right)
                    else:
                        q.append(None)
                else:
                    temp.append(node)

            if not self.SymCheck(temp):
                return False
            else:
                temp = []

        return True