题目：

题解：

func isSymmetric(root *TreeNode) bool {u, v := root, rootq := []*TreeNode{}q = append(q, u)q = append(q, v)for len(q) > 0 {u, v = q[0], q[1]q = q[2:]if u == nil && v == nil {continue}if u == nil || v == nil {return false}if u.Val != v.Val {return false}q = append(q, u.Left)q = append(q, v.Right)q = append(q, u.Right)q = append(q, v.Left)}return true
}