199. Binary Tree Right Side View

Given a binary tree, imagine yourself standing on the right side of it, return the values of the nodes you can see ordered from top to bottom.

Example:

Input:  [1,2,3,null,5,null,4]
Output:  [1, 3, 4]
Explanation:
   1            <---
 /   \
2     3         <---
 \     \
  5     4       <---

# @lc code=start
using LeetCode

function right_side_view(root::TreeNode{Int})::Vector{Int}
    q = Queue{Pair{TreeNode{Int}, Int}}()
    res = Int[]
    enqueue!(q, Pair(root, 1))
    while !isempty(q)
        nd, layer = dequeue!(q)
        (nd.left !== nothing) && enqueue!(q, Pair(nd.left, layer + 1))
        (nd.right !== nothing) && enqueue!(q, Pair(nd.right, layer + 1))
        (isempty(q) || layer < first(q).second) && (push!(res, nd.val))
    end
    res
end
# @lc code=end

right_side_view (generic function with 1 method)

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