feat: validate-binary-search-tree solution

Author: YeomChaeeun

validate-binary-search-tree/YeomChaeeun.ts

@@ -0,0 +1,28 @@
+/**
+ * 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 {
+    if (!root) return true;
+    
+    function isValid(node: TreeNode | null, min: number, max: number): boolean {
+        if (!node) return true;
+        if (node.val <= min || node.val >= max) return false;
+        
+        return isValid(node.left, min, node.val) && 
+               isValid(node.right, node.val, max)
+    }
+
+    // 초기 호출 (루트 노드의 범위는 무한대)
+    return isValid(root, -Infinity, Infinity)
+}