[Linked List] Add a solution to Convert Sorted List to Binary Search …

LinkedList/sortedListToBST.swift

@@ -0,0 +1,57 @@
+/**
+ * Question Link: https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/
+ * Primary idea: Convert the linked list to array, handle array using Divide and Conqure
+ * Time Complexity Per Action: O(N), Space Complexity: O(N)
+ *
+ */
+
+ /**
+ * Definition for singly-linked list.
+ * public class ListNode {
+ *     public var val: Int
+ *     public var next: ListNode?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.next = nil
+ *     }
+ * }
+ */
+/**
+ * Definition for a binary tree node.
+ * public class TreeNode {
+ *     public var val: Int
+ *     public var left: TreeNode?
+ *     public var right: TreeNode?
+ *     public init(_ val: Int) {
+ *         self.val = val
+ *         self.left = nil
+ *         self.right = nil
+ *     }
+ * }
+ */
+class Solution {
+    func sortedListToBST(_ head: ListNode?) -> TreeNode? {
+        var sortedArr: [Int] = []
+
+        var cur = head
+        while cur != nil {
+            sortedArr.append(cur!.val)
+            cur = cur!.next
+        }
+
+        return _helper(sortedArr, 0, sortedArr.count - 1)
+    }
+
+    private func _helper(_ sortedArr: [Int], _ left: Int, _ right: Int) -> TreeNode? {
+        guard left <= right else { return nil }
+
+        let mid = left + (right - left) >> 1
+
+        let root = TreeNode(sorted[mid])
+
+        root.left = _helper(sortedArr, left, mid - 1)
+        root.right = _helper(sortedArr, mid + 1, right)
+
+        return root
+    }
+}

README.md

@@ -149,6 +149,7 @@
 [Partition List](https://leetcode.com/problems/partition-list/)| [Swift](./LinkedList/PartitionList.swift)| Medium| O(n)| O(1)|
 [LRU Cache](https://leetcode.com/problems/lru-cache/) | [Swift](./LinkedList/LRUCache.swift) | Hard| O(1)| O(1)|
 [LFU Cache](https://leetcode.com/problems/lfu-cache/) | [Swift](./LinkedList/LFUCache.swift) | Hard| O(1)| O(1)|
+[Convert Sorted List to Binary Search Tree](https://leetcode.com/problems/convert-sorted-list-to-binary-search-tree/) | [Swift](./LinkedList/sortedListToBST) | Medium| O(n)| O(n)|
 
 ## Stack
 | Title | Solution | Difficulty | Time | Space |
@@ -762,7 +763,7 @@
 |	[Swift](./Tree/PathSum.swift)	|	112	|	[Path Sum](https://oj.leetcode.com/problems/path-sum/)	| Easy	|
 |	[Swift](./Tree/MinimumDepthOfBinaryTree.swift)	|	111	|	[Minimum Depth of Binary Tree](https://oj.leetcode.com/problems/minimum-depth-of-binary-tree/)	| Easy	|
 |	[Swift](./Tree/BalancedBinaryTree.swift)	|	110	|	[Balanced Binary Tree](https://oj.leetcode.com/problems/balanced-binary-tree/)	| Easy	|
-|		|	109	|	[Convert Sorted List to Binary Search Tree](https://oj.leetcode.com/problems/convert-sorted-list-to-binary-search-tree/)	| Medium	|
+|	[Swift](./LinkedList/sortedListToBST)	 |	109	|	[Convert Sorted List to Binary Search Tree](https://oj.leetcode.com/problems/convert-sorted-list-to-binary-search-tree/)	| Medium	|
 |	[Swift](./Tree/ConvertSortedArrayBinarySearchTree.swift)	|	108	|	[Convert Sorted Array to Binary Search Tree](https://oj.leetcode.com/problems/convert-sorted-array-to-binary-search-tree/)	| Medium	|
 |	[Swift](./Tree/BinaryTreeLevelOrderTraversalII.swift)	|	107	|	[Binary Tree Level Order Traversal II](https://oj.leetcode.com/problems/binary-tree-level-order-traversal-ii/)	| Easy	|
 |	[Swift](./Tree/ConstructBinaryTreeInorderPostorder.swift)	|	106	|	[Construct Binary Tree from Inorder and Postorder Traversal](https://oj.leetcode.com/problems/construct-binary-tree-from-inorder-and-postorder-traversal/)	| Medium	|