feat(leetcode): add No.1382

Author: mickey0524

1382.Balance-a-Binary-Search-Tree.java

@@ -0,0 +1,43 @@
+// https://leetcode.com/problems/balance-a-binary-search-tree/
+// algorithms
+// Easy (74.31%)
+// Total Accepted: 5,928
+// Total Submissions: 7,977
+
+
+/**
+ * Definition for a binary tree node. public class TreeNode { int val; TreeNode
+ * left; TreeNode right; TreeNode(int x) { val = x; } }
+ */
+class Solution {
+    public TreeNode balanceBST(TreeNode root) {
+        ArrayList<TreeNode> l = new ArrayList<>();
+        traversalTree(root, l);
+
+        return buildBalanceBST(l, 0, l.size() - 1);
+    }
+
+    private void traversalTree(TreeNode root, ArrayList<TreeNode> l) {
+        if (root == null) {
+            return;
+        }
+
+        traversalTree(root.left, l);
+        l.add(root);
+        traversalTree(root.right, l);
+    }
+
+    private TreeNode buildBalanceBST(ArrayList<TreeNode> l, int left, int right) {
+        if (right < left) {
+            return null;
+        }
+
+        int mid = left + (right - left) / 2;
+        TreeNode root = l.get(mid);
+        root.left = buildBalanceBST(l, left, mid - 1);
+        root.right = buildBalanceBST(l, mid + 1, right);
+
+        return root;
+    }
+
+}