Time: 201 ms (16.53%), Space: 37.2 MB (80.13%) - LeetHub

Author: hajin-kim

0098-validate-binary-search-tree/0098-validate-binary-search-tree.kt

@@ -0,0 +1,24 @@
+/**
+ * Example:
+ * var ti = TreeNode(5)
+ * var v = ti.`val`
+ * Definition for a binary tree node.
+ * class TreeNode(var `val`: Int) {
+ *     var left: TreeNode? = null
+ *     var right: TreeNode? = null
+ * }
+ */
+class Solution {
+    fun isValidBST(root: TreeNode?): Boolean {
+        return root.isInRange(Long.MIN_VALUE, Long.MAX_VALUE)
+    }
+
+    private fun TreeNode?.isInRange(min: Long, max: Long): Boolean {
+        this ?: return true
+
+        if (`val` !in (min + 1)..<max)
+            return false
+
+        return left.isInRange(min, `val`.toLong()) && right.isInRange(`val`.toLong(), max)
+    }
+}