Create 1382-balance-a-binary-search-tree.js

Author: everthis

1382-balance-a-binary-search-tree.js

@@ -0,0 +1,33 @@
+/**
+ * Definition for a binary tree node.
+ * function TreeNode(val, left, right) {
+ *     this.val = (val===undefined ? 0 : val)
+ *     this.left = (left===undefined ? null : left)
+ *     this.right = (right===undefined ? null : right)
+ * }
+ */
+/**
+ * @param {TreeNode} root
+ * @return {TreeNode}
+ */
+const balanceBST = function(root) {
+  const arr = []
+  inOrder(root, arr)
+  return constructBST(arr, 0, arr.length - 1)
+};
+
+function inOrder(node, arr) {
+  if(node == null) return
+  inOrder(node.left, arr)
+  arr.push(node.val)
+  inOrder(node.right, arr)
+}
+
+function constructBST(arr, start, end) {
+  if(start > end) return null
+  const mid = start + ((end - start) >> 1)
+  const node = new TreeNode(arr[mid])
+  node.left = constructBST(arr, start, mid - 1)
+  node.right = constructBST(arr, mid + 1, end)
+  return node
+}