validate binary search tree solved

Author: sora0319

validate-binary-search-tree/sora0319.java

@@ -0,0 +1,13 @@
+class Solution {
+    public boolean isValidBST(TreeNode root) {
+        if(root==null||(root.left==null&&root.right==null)) return true;
+        return isvalid(root,Long.MIN_VALUE,Long.MAX_VALUE);
+    }
+    public boolean isvalid(TreeNode root,long min,long max)
+    {
+        if(root==null) return true;
+        if(root.val<=min||root.val>=max) return false;
+        return isvalid(root.left,min,root.val)&&isvalid(root.right,root.val,max);
+    }
+}
+