Merge pull request neetcode-gh#874 from MaratKhakim/102-BT-Level-Order-Kt

Kotlin: 102. Binary Tree Level Order Traversal

Author: Ahmad-A0

kotlin/102-Binary-Tree-Level-Order-Traversal.kt

@@ -0,0 +1,41 @@
+/**
+ * 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 {
+    fun levelOrder(root: TreeNode?): List<List<Int>> {
+        val res = mutableListOf<List<Int>>()
+
+        if (root == null)
+            return res
+
+        val queue = LinkedList<TreeNode>()
+        queue.add(root)
+
+        while (!queue.isEmpty()) {
+            val size = queue.size
+            val level = mutableListOf<Int>()
+
+            repeat(size) {
+                val node = queue.poll()
+                level.add(node.`val`)
+
+                if (node.left != null)
+                    queue.add(node.left)
+
+                if (node.right != null)
+                    queue.add(node.right)
+            }
+
+            res.add(level)
+        }
+
+        return res
+    }
+}