add Binary Tree Level Order Traversal solution

Author: HoonDongKang

binary-tree-level-order-traversal/HoonDongKang.ts

@@ -0,0 +1,41 @@
+/**
+ * [Problem]: [102] Binary Tree Level Order Traversal
+ * (https://leetcode.com/problems/binary-tree-level-order-traversal/description/)
+ */
+
+class TreeNode {
+    val: number;
+    left: TreeNode | null;
+    right: TreeNode | null;
+    constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+        this.val = val === undefined ? 0 : val;
+        this.left = left === undefined ? null : left;
+        this.right = right === undefined ? null : right;
+    }
+}
+
+// 시간복잡도 O(n)
+// 공간복잡도 O(n)
+function levelOrder(root: TreeNode | null): number[][] {
+    if (!root) return [];
+
+    const result: number[][] = [];
+    const queue: TreeNode[] = [root];
+
+    while (queue.length > 0) {
+        const level = queue.length;
+        const values: number[] = [];
+
+        for (let i = 0; i < level; i++) {
+            const node = queue.shift()!;
+            values.push(node.val);
+
+            if (node.left) queue.push(node.left);
+            if (node.right) queue.push(node.right);
+        }
+
+        result.push(values);
+    }
+
+    return result;
+}