validate-binary-search-tree

Author: sooooo-an

validate-binary-search-tree/sooooo-an.ts

@@ -0,0 +1,18 @@
+function isValidBST(root: TreeNode | null): boolean {
+  return validateBSTHelper(root, -Infinity, Infinity);
+}
+
+const validateBSTHelper = (
+  root: TreeNode | null,
+  minValue: number,
+  maxValue: number
+): boolean => {
+  if (root === null) {
+    return true;
+  }
+  if (root.val <= minValue || root.val >= maxValue) {
+    return false;
+  }
+  const leftIsValid = validateBSTHelper(root.left, minValue, root.val);
+  return leftIsValid && validateBSTHelper(root.right, root.val, maxValue);
+};