Method isSymmetric3

leetcode/101. Symmetric Tree.py:64–74

(self, root)

    # iterative(DFS)
    def isSymmetric3(self, root):
        if root:
            stack = [(root.left, root.right)]
            while len(stack) > 0:
                p, q = stack.pop()
                if p and q and p.val == q.val:
                    stack.append((p.left, q.right))
                    stack.append((p.right, q.left))
                elif p != q:
                    return False
        return True