101. Symmetric Tree

Given a binary tree, check whether it is a mirror of itself (ie, symmetric around its center).

For example, this binary tree [1,2,2,3,4,4,3] is symmetric:

    1
   / \
  2   2
 / \ / \
3  4 4  3

But the following [1,2,2,null,3,null,3] is not:

    1
   / \
  2   2
   \   \
   3    3

Follow up: Solve it both recursively and iteratively.

# @lc code=start
using LeetCode

is_symmetric_tree(root::TreeNode{Int})::Bool = is_mirror_tree(root.left, root.right)
function is_mirror_tree(
    t1::Union{TreeNode{Int},Nothing}, t2::Union{TreeNode{Int},Nothing}
)::Bool
    isnothing(t1) && isnothing(t2) && return true
    (isnothing(t1) || isnothing(t2)) && return false
    t1.val != t2.val && return false
    return is_mirror_tree(t1.left, t2.right) && is_mirror_tree(t1.right, t2.left)
end
# @lc code=end

is_mirror_tree (generic function with 1 method)

This page was generated using DemoCards.jl and Literate.jl.