solved: 108

Author: ryoppippi

code/108.convert-sorted-array-to-binary-search-tree.ts

@@ -0,0 +1,41 @@
+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;
+  }
+}
+
+// @leet start
+/**
+ * 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 sortedArrayToBST(nums: number[]): TreeNode | null {
+  if (nums.length === 0) return null;
+
+  /* array is sorted, so define the root, which is the middle element */
+  const rootIndex = Math.floor(nums.length / 2);
+  const root = new TreeNode(nums[rootIndex]);
+
+  /* recursively create left & right */
+  root.left = sortedArrayToBST(nums.slice(0, rootIndex));
+  root.right = sortedArrayToBST(nums.slice(rootIndex + 1));
+
+  return root;
+}
+// @leet end
+