diff --git a/validate-binary-search-tree/sol.go b/validate-binary-search-tree/sol.go
new file mode 100644
index 0000000..d8cb80a
--- /dev/null
+++ b/validate-binary-search-tree/sol.go
@@ -0,0 +1,28 @@
+package main
+
+type TreeNode struct {
+	Val   int
+	Left  *TreeNode
+	Right *TreeNode
+}
+
+/**
+ * Definition for a binary tree node.
+ * type TreeNode struct {
+ *     Val int
+ *     Left *TreeNode
+ *     Right *TreeNode
+ * }
+ */
+func isValidSubBST(root *TreeNode, min, max int) bool {
+	if root == nil {
+		return true
+	}
+	if root.Val < min || root.Val > max {
+		return false
+	}
+	return isValidSubBST(root.Left, min, root.Val-1) && isValidSubBST(root.Right, root.Val+1, max)
+}
+func isValidBST(root *TreeNode) bool {
+	return isValidSubBST(root, -1<<31, 1<<31)
+}