LeetCode Notes [51]: Kotlin solution with a queue used

John Lu

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Mar 13, 2023

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Problem

Implementation

class Solution {
    fun levelOrder(root: TreeNode?): List<List<Int>> {
        val result = mutableListOf<List<Int>>()
        val queue: Queue<TreeNode> = LinkedList()
        root?.let { queue.add(it) }
        while (queue.isNotEmpty()) {
            val level = mutableListOf<Int>()
            for (i in 0 until queue.size) {
                val node = queue.poll()
                level.add(node.`val`)
                node.left?.let { queue.add(it) }
                node.right?.let { queue.add(it) }
            }
            result.add(level)
        }
        return result
    }
}

Complexity Analysis

• Time Complexity: O(n)
• Space Complexity: O(n)