diff --git a/problems/binary-tree-level-order-traversal.kt b/problems/binary-tree-level-order-traversal.kt new file mode 100644 index 0000000..21ca888 --- /dev/null +++ b/problems/binary-tree-level-order-traversal.kt @@ -0,0 +1,27 @@ +/** + * Example: + * var ti = TreeNode(5) + * var v = ti.`val` + * Definition for a binary tree node. + * class TreeNode(var `val`: Int) { + * var left: TreeNode? = null + * var right: TreeNode? = null + * } + */ +class Solution { + private fun levelOrder(root: TreeNode?, levels: MutableList>, level: Int): MutableList> { + if (root == null) { + return levels + } + + if (level + 1 > levels.size) { + levels.add(mutableListOf()) + } + + levels[level].add(root.`val`) + levelOrder(root.left, levels, level + 1) + return levelOrder(root.right, levels, level + 1) + } + + fun levelOrder(root: TreeNode?): List> = levelOrder(root, mutableListOf>(), 0) +}