vault backup: 2026-05-30 16:02:33

leetcode/note/hard/30_substring_with_concatenation_of_all_words.md

@@ -0,0 +1,13 @@
+---
+id: 30
+title: Substring with Concatenation of All Words
+difficulty: Hard
+tags:
+  - hash-table
+  - string
+  - sliding-window
+status: unsolve
+date_solved: 2026-05-26
+leetcode_url: https://leetcode.com/problems/substring-with-concatenation-of-all-words/
+review_needed: false
+---

leetcode/note/hard/381_insert_delete_getrandom_o1_duplicates_allowed.md

@@ -0,0 +1,15 @@
+---
+id: 381
+title: Insert Delete GetRandom O(1) - Duplicates allowed
+difficulty: Hard
+tags:
+  - array
+  - hash-table
+  - math
+  - randomized
+  - design
+status: unsolve
+date_solved: 2026-05-26
+leetcode_url: https://leetcode.com/problems/insert-delete-getrandom-o1-duplicates-allowed/
+review_needed: false
+---

leetcode/note/hard/41_first_missing_positive.md

@@ -0,0 +1,12 @@
+---
+id: 41
+title: First Missing Positive
+difficulty: Hard
+tags:
+  - array
+  - hash-table
+status: unsolve
+date_solved: 2026-05-26
+leetcode_url: https://leetcode.com/problems/first-missing-positive/
+review_needed: false
+---