LeetCode-in-TypeScript · javadev · Apr 7, 2025 · Apr 7, 2025 · Apr 7, 2025 · Apr 7, 2025
diff --git a/README.md b/README.md
@@ -776,6 +776,7 @@ TypeScript-based LeetCode algorithm problem solutions, regularly updated.
 
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
+| 0108 |[Convert Sorted Array to Binary Search Tree](src/main/ts/g0101_0200/s0108_convert_sorted_array_to_binary_search_tree/solution.ts)| Easy | Top_Interview_Questions, Array, Tree, Binary_Tree, Binary_Search_Tree, Divide_and_Conquer | 0 | 100.00
 | 0230 |[Kth Smallest Element in a BST](src/main/ts/g0201_0300/s0230_kth_smallest_element_in_a_bst/solution.ts)| Medium | Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree, Big_O_Time_O(n)_Space_O(n) | 0 | 100.00
 
 #### Day 10 Graph/BFS/DFS
@@ -945,6 +946,8 @@ TypeScript-based LeetCode algorithm problem solutions, regularly updated.
 |-|-|-|-|-|-
 | 0094 |[Binary Tree Inorder Traversal](src/main/ts/g0001_0100/s0094_binary_tree_inorder_traversal/solution.ts)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Big_O_Time_O(n)_Space_O(n) | 0 | 100.00
 | 0102 |[Binary Tree Level Order Traversal](src/main/ts/g0101_0200/s0102_binary_tree_level_order_traversal/solution.ts)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(N) | 0 | 100.00
+| 0103 |[Binary Tree Zigzag Level Order Traversal](src/main/ts/g0101_0200/s0103_binary_tree_zigzag_level_order_traversal/solution.ts)| Medium | Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree | 0 | 100.00
+| 0108 |[Convert Sorted Array to Binary Search Tree](src/main/ts/g0101_0200/s0108_convert_sorted_array_to_binary_search_tree/solution.ts)| Easy | Top_Interview_Questions, Array, Tree, Binary_Tree, Binary_Search_Tree, Divide_and_Conquer | 0 | 100.00
 | 0543 |[Diameter of Binary Tree](src/main/ts/g0501_0600/s0543_diameter_of_binary_tree/solution.ts)| Easy | Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n) | 1 | 87.16
 | 0226 |[Invert Binary Tree](src/main/ts/g0201_0300/s0226_invert_binary_tree/solution.ts)| Easy | Top_100_Liked_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n) | 0 | 100.00
 | 0104 |[Maximum Depth of Binary Tree](src/main/ts/g0101_0200/s0104_maximum_depth_of_binary_tree/solution.ts)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(H) | 0 | 100.00
@@ -1096,7 +1099,9 @@ TypeScript-based LeetCode algorithm problem solutions, regularly updated.
 | 0226 |[Invert Binary Tree](src/main/ts/g0201_0300/s0226_invert_binary_tree/solution.ts)| Easy | Top_100_Liked_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n) | 0 | 100.00
 | 0101 |[Symmetric Tree](src/main/ts/g0101_0200/s0101_symmetric_tree/solution.ts)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(log(N)) | 0 | 100.00
 | 0105 |[Construct Binary Tree from Preorder and Inorder Traversal](src/main/ts/g0101_0200/s0105_construct_binary_tree_from_preorder_and_inorder_traversal/solution.ts)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer, Big_O_Time_O(N)_Space_O(N) | 2 | 93.38
+| 0106 |[Construct Binary Tree from Inorder and Postorder Traversal](src/main/ts/g0101_0200/s0106_construct_binary_tree_from_inorder_and_postorder_traversal/solution.ts)| Medium | Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer | 1 | 98.78
 | 0114 |[Flatten Binary Tree to Linked List](src/main/ts/g0101_0200/s0114_flatten_binary_tree_to_linked_list/solution.ts)| Medium | Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Linked_List, Big_O_Time_O(N)_Space_O(N) | 0 | 100.00
+| 0112 |[Path Sum](src/main/ts/g0101_0200/s0112_path_sum/solution.ts)| Easy | Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 0 | 100.00
 | 0124 |[Binary Tree Maximum Path Sum](src/main/ts/g0101_0200/s0124_binary_tree_maximum_path_sum/solution.ts)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Depth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(N) | 2 | 71.11
 | 0236 |[Lowest Common Ancestor of a Binary Tree](src/main/ts/g0201_0300/s0236_lowest_common_ancestor_of_a_binary_tree/solution.ts)| Medium | Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n) | 61 | 75.97
 
@@ -1105,6 +1110,7 @@ TypeScript-based LeetCode algorithm problem solutions, regularly updated.
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
 | 0102 |[Binary Tree Level Order Traversal](src/main/ts/g0101_0200/s0102_binary_tree_level_order_traversal/solution.ts)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(N)_Space_O(N) | 0 | 100.00
+| 0103 |[Binary Tree Zigzag Level Order Traversal](src/main/ts/g0101_0200/s0103_binary_tree_zigzag_level_order_traversal/solution.ts)| Medium | Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree | 0 | 100.00
 
 #### Top Interview 150 Binary Search Tree
 
@@ -1147,6 +1153,7 @@ TypeScript-based LeetCode algorithm problem solutions, regularly updated.
 
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
+| 0108 |[Convert Sorted Array to Binary Search Tree](src/main/ts/g0101_0200/s0108_convert_sorted_array_to_binary_search_tree/solution.ts)| Easy | Top_Interview_Questions, Array, Tree, Binary_Tree, Binary_Search_Tree, Divide_and_Conquer | 0 | 100.00
 | 0148 |[Sort List](src/main/ts/g0101_0200/s0148_sort_list/solution.ts)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Sorting, Two_Pointers, Linked_List, Divide_and_Conquer, Merge_Sort, Big_O_Time_O(log(N))_Space_O(log(N)) | 36 | 44.94
 | 0023 |[Merge k Sorted Lists](src/main/ts/g0001_0100/s0023_merge_k_sorted_lists/solution.ts)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Heap_Priority_Queue, Linked_List, Divide_and_Conquer, Merge_Sort, Big_O_Time_O(k\*n\*log(k))_Space_O(log(k)) | 4 | 97.65
 
@@ -1207,6 +1214,7 @@ TypeScript-based LeetCode algorithm problem solutions, regularly updated.
 | 0064 |[Minimum Path Sum](src/main/ts/g0001_0100/s0064_minimum_path_sum/solution.ts)| Medium | Top_100_Liked_Questions, Array, Dynamic_Programming, Matrix, Big_O_Time_O(m\*n)_Space_O(m\*n) | 4 | 70.73
 | 0063 |[Unique Paths II](src/main/ts/g0001_0100/s0063_unique_paths_ii/solution.ts)| Medium | Array, Dynamic_Programming, Matrix | 0 | 100.00
 | 0005 |[Longest Palindromic Substring](src/main/ts/g0001_0100/s0005_longest_palindromic_substring/solution.ts)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, String, Dynamic_Programming, Big_O_Time_O(n)_Space_O(n) | 8 | 99.14
+| 0097 |[Interleaving String](src/main/ts/g0001_0100/s0097_interleaving_string/solution.ts)| Medium | String, Dynamic_Programming | 43 | 97.65
 | 0072 |[Edit Distance](src/main/ts/g0001_0100/s0072_edit_distance/solution.ts)| Medium | Top_100_Liked_Questions, String, Dynamic_Programming, Big_O_Time_O(n^2)_Space_O(n2) | 6 | 93.83
 | 0221 |[Maximal Square](src/main/ts/g0201_0300/s0221_maximal_square/solution.ts)| Medium | Array, Dynamic_Programming, Matrix, Big_O_Time_O(m\*n)_Space_O(m\*n) | 18 | 59.02
 
@@ -1286,6 +1294,7 @@ TypeScript-based LeetCode algorithm problem solutions, regularly updated.
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
 | 0226 |[Invert Binary Tree](src/main/ts/g0201_0300/s0226_invert_binary_tree/solution.ts)| Easy | Top_100_Liked_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Big_O_Time_O(n)_Space_O(n) | 0 | 100.00
+| 0112 |[Path Sum](src/main/ts/g0101_0200/s0112_path_sum/solution.ts)| Easy | Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree | 0 | 100.00
 
 #### Day 13 Tree
 
@@ -1393,7 +1402,9 @@ TypeScript-based LeetCode algorithm problem solutions, regularly updated.
 
 | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- --> | <!-- -->
 |-|-|-|-|-|-
+| 0108 |[Convert Sorted Array to Binary Search Tree](src/main/ts/g0101_0200/s0108_convert_sorted_array_to_binary_search_tree/solution.ts)| Easy | Top_Interview_Questions, Array, Tree, Binary_Tree, Binary_Search_Tree, Divide_and_Conquer | 0 | 100.00
 | 0105 |[Construct Binary Tree from Preorder and Inorder Traversal](src/main/ts/g0101_0200/s0105_construct_binary_tree_from_preorder_and_inorder_traversal/solution.ts)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer, Big_O_Time_O(N)_Space_O(N) | 2 | 93.38
+| 0103 |[Binary Tree Zigzag Level Order Traversal](src/main/ts/g0101_0200/s0103_binary_tree_zigzag_level_order_traversal/solution.ts)| Medium | Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree | 0 | 100.00
 
 #### Day 16 Tree
 
@@ -1697,11 +1708,16 @@ TypeScript-based LeetCode algorithm problem solutions, regularly updated.
 | 0124 |[Binary Tree Maximum Path Sum](src/main/ts/g0101_0200/s0124_binary_tree_maximum_path_sum/solution.ts)| Hard | Top_100_Liked_Questions, Top_Interview_Questions, Dynamic_Programming, Depth_First_Search, Tree, Binary_Tree, Udemy_Tree_Stack_Queue, Top_Interview_150_Binary_Tree_General, Big_O_Time_O(N)_Space_O(N) | 2 | 71.11
 | 0121 |[Best Time to Buy and Sell Stock](src/main/ts/g0101_0200/s0121_best_time_to_buy_and_sell_stock/solution.ts)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Array, Dynamic_Programming, Data_Structure_I_Day_3_Array, Dynamic_Programming_I_Day_7, Level_1_Day_5_Greedy, Udemy_Arrays, Top_Interview_150_Array/String, Big_O_Time_O(N)_Space_O(1) | 1 | 96.44
 | 0114 |[Flatten Binary Tree to Linked List](src/main/ts/g0101_0200/s0114_flatten_binary_tree_to_linked_list/solution.ts)| Medium | Top_100_Liked_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Linked_List, Udemy_Linked_List, Top_Interview_150_Binary_Tree_General, Big_O_Time_O(N)_Space_O(N) | 0 | 100.00
+| 0112 |[Path Sum](src/main/ts/g0101_0200/s0112_path_sum/solution.ts)| Easy | Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_I_Day_12_Tree, Top_Interview_150_Binary_Tree_General | 0 | 100.00
+| 0108 |[Convert Sorted Array to Binary Search Tree](src/main/ts/g0101_0200/s0108_convert_sorted_array_to_binary_search_tree/solution.ts)| Easy | Top_Interview_Questions, Array, Tree, Binary_Tree, Binary_Search_Tree, Divide_and_Conquer, Data_Structure_II_Day_15_Tree, Level_2_Day_9_Binary_Search_Tree, Udemy_Tree_Stack_Queue, Top_Interview_150_Divide_and_Conquer | 0 | 100.00
+| 0106 |[Construct Binary Tree from Inorder and Postorder Traversal](src/main/ts/g0101_0200/s0106_construct_binary_tree_from_inorder_and_postorder_traversal/solution.ts)| Medium | Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer, Top_Interview_150_Binary_Tree_General | 1 | 98.78
 | 0105 |[Construct Binary Tree from Preorder and Inorder Traversal](src/main/ts/g0101_0200/s0105_construct_binary_tree_from_preorder_and_inorder_traversal/solution.ts)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Array, Hash_Table, Tree, Binary_Tree, Divide_and_Conquer, Data_Structure_II_Day_15_Tree, Top_Interview_150_Binary_Tree_General, Big_O_Time_O(N)_Space_O(N) | 2 | 93.38
 | 0104 |[Maximum Depth of Binary Tree](src/main/ts/g0101_0200/s0104_maximum_depth_of_binary_tree/solution.ts)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_I_Day_11_Tree, Programming_Skills_I_Day_10_Linked_List_and_Tree, Udemy_Tree_Stack_Queue, Top_Interview_150_Binary_Tree_General, Big_O_Time_O(N)_Space_O(H) | 0 | 100.00
+| 0103 |[Binary Tree Zigzag Level Order Traversal](src/main/ts/g0101_0200/s0103_binary_tree_zigzag_level_order_traversal/solution.ts)| Medium | Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_II_Day_15_Tree, Udemy_Tree_Stack_Queue, Top_Interview_150_Binary_Tree_BFS | 0 | 100.00
 | 0102 |[Binary Tree Level Order Traversal](src/main/ts/g0101_0200/s0102_binary_tree_level_order_traversal/solution.ts)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_I_Day_11_Tree, Level_1_Day_6_Tree, Udemy_Tree_Stack_Queue, Top_Interview_150_Binary_Tree_BFS, Big_O_Time_O(N)_Space_O(N) | 0 | 100.00
 | 0101 |[Symmetric Tree](src/main/ts/g0101_0200/s0101_symmetric_tree/solution.ts)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Breadth_First_Search, Tree, Binary_Tree, Data_Structure_I_Day_11_Tree, Level_2_Day_15_Tree, Top_Interview_150_Binary_Tree_General, Big_O_Time_O(N)_Space_O(log(N)) | 0 | 100.00
 | 0098 |[Validate Binary Search Tree](src/main/ts/g0001_0100/s0098_validate_binary_search_tree/solution.ts)| Medium | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Binary_Search_Tree, Data_Structure_I_Day_14_Tree, Level_1_Day_8_Binary_Search_Tree, Udemy_Tree_Stack_Queue, Top_Interview_150_Binary_Search_Tree, Big_O_Time_O(N)_Space_O(log(N)) | 0 | 100.00
+| 0097 |[Interleaving String](src/main/ts/g0001_0100/s0097_interleaving_string/solution.ts)| Medium | String, Dynamic_Programming, Top_Interview_150_Multidimensional_DP | 43 | 97.65
 | 0096 |[Unique Binary Search Trees](src/main/ts/g0001_0100/s0096_unique_binary_search_trees/solution.ts)| Medium | Dynamic_Programming, Math, Tree, Binary_Tree, Binary_Search_Tree, Dynamic_Programming_I_Day_11, Big_O_Time_O(n)_Space_O(1) | 0 | 100.00
 | 0094 |[Binary Tree Inorder Traversal](src/main/ts/g0001_0100/s0094_binary_tree_inorder_traversal/solution.ts)| Easy | Top_100_Liked_Questions, Top_Interview_Questions, Depth_First_Search, Tree, Binary_Tree, Stack, Data_Structure_I_Day_10_Tree, Udemy_Tree_Stack_Queue, Big_O_Time_O(n)_Space_O(n) | 0 | 100.00
 | 0092 |[Reverse Linked List II](src/main/ts/g0001_0100/s0092_reverse_linked_list_ii/solution.ts)| Medium | Linked_List, Top_Interview_150_Linked_List | 0 | 100.00

diff --git a/src/main/ts/g0001_0100/s0097_interleaving_string/readme.md b/src/main/ts/g0001_0100/s0097_interleaving_string/readme.md
@@ -0,0 +1,42 @@
+97\. Interleaving String
+
+Medium
+
+Given strings `s1`, `s2`, and `s3`, find whether `s3` is formed by an **interleaving** of `s1` and `s2`.
+
+An **interleaving** of two strings `s` and `t` is a configuration where they are divided into **non-empty** substrings such that:
+
+*   <code>s = s<sub>1</sub> + s<sub>2</sub> + ... + s<sub>n</sub></code>
+*   <code>t = t<sub>1</sub> + t<sub>2</sub> + ... + t<sub>m</sub></code>
+*   `|n - m| <= 1`
+*   The **interleaving** is <code>s<sub>1</sub> + t<sub>1</sub> + s<sub>2</sub> + t<sub>2</sub> + s<sub>3</sub> + t<sub>3</sub> + ...</code> or <code>t<sub>1</sub> + s<sub>1</sub> + t<sub>2</sub> + s<sub>2</sub> + t<sub>3</sub> + s<sub>3</sub> + ...</code>
+
+**Note:** `a + b` is the concatenation of strings `a` and `b`.
+
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2020/09/02/interleave.jpg)
+
+**Input:** s1 = "aabcc", s2 = "dbbca", s3 = "aadbbcbcac"
+
+**Output:** true 
+
+**Example 2:**
+
+**Input:** s1 = "aabcc", s2 = "dbbca", s3 = "aadbbbaccc"
+
+**Output:** false 
+
+**Example 3:**
+
+**Input:** s1 = "", s2 = "", s3 = ""
+
+**Output:** true 
+
+**Constraints:**
+
+*   `0 <= s1.length, s2.length <= 100`
+*   `0 <= s3.length <= 200`
+*   `s1`, `s2`, and `s3` consist of lowercase English letters.
+
+**Follow up:** Could you solve it using only `O(s2.length)` additional memory space?
diff --git a/src/main/ts/g0001_0100/s0097_interleaving_string/solution.ts b/src/main/ts/g0001_0100/s0097_interleaving_string/solution.ts
@@ -0,0 +1,38 @@
+// #Medium #String #Dynamic_Programming #Top_Interview_150_Multidimensional_DP
+// #2025_04_05_Time_43_ms_(97.65%)_Space_58.17_MB_(61.77%)
+
+function isInterleave(s1: string, s2: string, s3: string): boolean {
+    if (s3.length !== (s1.length + s2.length)) {
+        return false
+    }
+    const cache: boolean[][] = Array.from({ length: s1.length + 1 }, () => Array(s2.length + 1).fill(null))
+    return isInterleaveHelper(s1, s2, s3, 0, 0, 0, cache)
+}
+
+function isInterleaveHelper(
+    s1: string,
+    s2: string,
+    s3: string,
+    i1: number,
+    i2: number,
+    i3: number,
+    cache: boolean[][]
+): boolean {
+    if (cache[i1][i2] !== null) {
+        return cache[i1][i2]
+    }
+    if (i1 === s1.length && i2 === s2.length && i3 === s3.length) {
+        return true
+    }
+    let result = false
+    if (i1 < s1.length && s1.charAt(i1) === s3.charAt(i3)) {
+        result = isInterleaveHelper(s1, s2, s3, i1 + 1, i2, i3 + 1, cache)
+    }
+    if (i2 < s2.length && s2.charAt(i2) === s3.charAt(i3)) {
+        result = result || isInterleaveHelper(s1, s2, s3, i1, i2 + 1, i3 + 1, cache)
+    }
+    cache[i1][i2] = result
+    return result
+}
+
+export { isInterleave }
diff --git a/src/main/ts/g0101_0200/s0103_binary_tree_zigzag_level_order_traversal/readme.md b/src/main/ts/g0101_0200/s0103_binary_tree_zigzag_level_order_traversal/readme.md
@@ -0,0 +1,30 @@
+103\. Binary Tree Zigzag Level Order Traversal
+
+Medium
+
+Given the `root` of a binary tree, return _the zigzag level order traversal of its nodes' values_. (i.e., from left to right, then right to left for the next level and alternate between).
+
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2021/02/19/tree1.jpg)
+
+**Input:** root = [3,9,20,null,null,15,7]
+
+**Output:** [[3],[20,9],[15,7]] 
+
+**Example 2:**
+
+**Input:** root = [1]
+
+**Output:** [[1]] 
+
+**Example 3:**
+
+**Input:** root = []
+
+**Output:** [] 
+
+**Constraints:**
+
+*   The number of nodes in the tree is in the range `[0, 2000]`.
+*   `-100 <= Node.val <= 100`
diff --git a/src/main/ts/g0101_0200/s0103_binary_tree_zigzag_level_order_traversal/solution.ts b/src/main/ts/g0101_0200/s0103_binary_tree_zigzag_level_order_traversal/solution.ts
@@ -0,0 +1,54 @@
+// #Medium #Top_Interview_Questions #Breadth_First_Search #Tree #Binary_Tree
+// #Data_Structure_II_Day_15_Tree #Udemy_Tree_Stack_Queue #Top_Interview_150_Binary_Tree_BFS
+// #2025_04_05_Time_0_ms_(100.00%)_Space_58.00_MB_(52.61%)
+
+import { TreeNode } from '../../com_github_leetcode/treenode'
+
+/**
+ * Definition for a binary tree node.
+ * 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)
+ *     }
+ * }
+ */
+function zigzagLevelOrder(root: TreeNode | null): number[][] {
+    const result: number[][] = []
+    if (root === null) {
+        return result
+    }
+    const q: (TreeNode | null)[] = [root, null]
+    let zig = true
+    let level: number[] = []
+    while (q.length > 0) {
+        const node = q.shift()
+        if (node === null) {
+            result.push(level)
+            zig = !zig
+            level = []
+            if (q.length > 0) {
+                q.push(null)
+            }
+        } else {
+            if (zig) {
+                level.push(node.val)
+            } else {
+                level.unshift(node.val)
+            }
+            if (node.left !== null) {
+                q.push(node.left)
+            }
+            if (node.right !== null) {
+                q.push(node.right)
+            }
+        }
+    }
+    return result
+}
+
+export { zigzagLevelOrder }
diff --git a/...0200/s0106_construct_binary_tree_from_inorder_and_postorder_traversal/readme.md b/...0200/s0106_construct_binary_tree_from_inorder_and_postorder_traversal/readme.md
@@ -0,0 +1,29 @@
+106\. Construct Binary Tree from Inorder and Postorder Traversal
+
+Medium
+
+Given two integer arrays `inorder` and `postorder` where `inorder` is the inorder traversal of a binary tree and `postorder` is the postorder traversal of the same tree, construct and return _the binary tree_.
+
+**Example 1:**
+
+![](https://assets.leetcode.com/uploads/2021/02/19/tree.jpg)
+
+**Input:** inorder = [9,3,15,20,7], postorder = [9,15,7,20,3]
+
+**Output:** [3,9,20,null,null,15,7] 
+
+**Example 2:**
+
+**Input:** inorder = [-1], postorder = [-1]
+
+**Output:** [-1] 
+
+**Constraints:**
+
+*   `1 <= inorder.length <= 3000`
+*   `postorder.length == inorder.length`
+*   `-3000 <= inorder[i], postorder[i] <= 3000`
+*   `inorder` and `postorder` consist of **unique** values.
+*   Each value of `postorder` also appears in `inorder`.
+*   `inorder` is **guaranteed** to be the inorder traversal of the tree.
+*   `postorder` is **guaranteed** to be the postorder traversal of the tree.