validate binary search tree solution

Author: hyer0705

validate-binary-search-tree/hyer0705.ts

@@ -0,0 +1,32 @@
+/**
+ * Definition for a binary tree node.
+ * class TreeNode {
+ *     val: number
+ *     left: TreeNode | null
+ *     right: TreeNode | null
+ *     constructor(val?: number, left?: TreeNode | null, right?: TreeNode | null) {
+ *         this.val = (val===undefined ? 0 : val)
+ *         this.left = (left===undefined ? null : left)
+ *         this.right = (right===undefined ? null : right)
+ *     }
+ * }
+ */
+
+function isValidBST(root: TreeNode | null): boolean {
+  const queue: [TreeNode, number, number][] = [[root, -Infinity, +Infinity]];
+
+  while (queue.length > 0) {
+    const [currentNode, minVal, maxVal] = queue.shift();
+
+    if (minVal >= currentNode.val || currentNode.val >= maxVal) return false;
+
+    if (currentNode.left) {
+      queue.push([currentNode.left, minVal, currentNode.val]);
+    }
+    if (currentNode.right) {
+      queue.push([currentNode.right, currentNode.val, maxVal]);
+    }
+  }
+
+  return true;
+}