226. Invert Binary Tree

Invert a binary tree.

Example:

Input:

     4
   /   \
  2     7
 / \   / \
1   3 6   9

Output:

     4
   /   \
  7     2
 / \   / \
9   6 3   1

Trivia: This problem was inspired by this original tweet by Max Howell:

Google: 90% of our engineers use the software you wrote (Homebrew), but you can't invert a binary tree on a whiteboard so f*** off.

# @lc code=start
using LeetCode

function invert_tree!(root::Union{TreeNode{Int},Nothing})::Union{TreeNode,Nothing}
    isnothing(root) && return nothing
    queue = [root]
    while !isempty(queue)
        node = popfirst!(queue)
        if !isnothing(node.left)
            push!(queue, node.left)
        end
        if !isnothing(node.right)
            push!(queue, node.right)
        end
        node.left, node.right = node.right, node.left
    end
    return root
end
# @lc code=end

invert_tree! (generic function with 1 method)

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