add new solutions

solutions/13/q1382/solution.go

@@ -0,0 +1,37 @@
+package q1382
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+func flatten(node *TreeNode, result *[]*TreeNode) {
+	if node == nil {
+		return
+	}
+	flatten(node.Left, result)
+	*result = append(*result, node)
+	flatten(node.Right, result)
+}
+
+func reconstruct(nodes []*TreeNode) *TreeNode {
+	if len(nodes) == 0 {
+		return nil
+	}
+	mid := len(nodes) / 2
+	root := nodes[mid]
+	root.Left = reconstruct(nodes[:mid])
+	root.Right = reconstruct(nodes[mid+1:])
+
+	return root
+}
+
+func balanceBST(root *TreeNode) *TreeNode {
+	nodes := make([]*TreeNode, 0, 128)
+	flatten(root, &nodes)
+
+	return reconstruct(nodes)
+}
+
+var _ = balanceBST