# interviews | Kevin Naughton Jr. | Knowledge Base | Instagit

Everything you need to know to get the job.

GitHub Stars: 64.9k

Repository: https://github.com/kdn251/interviews

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## Articles

### [How to Achieve O(1) Insert, Delete, and GetRandom Operations in a Collection](/kdn251/interviews/insert-delete-getrandom-o-1)

Learn how to achieve O(1) insert, delete, and getRandom operations using a HashMap and ArrayList with the swap-with-last technique. Optimize your collection performance.

- Tags: algorithm
- Published: 2026-03-04

### [Backtracking and Bit Manipulation Approaches for Generating Subsets](/kdn251/interviews/generate-subsets-backtracking-bit-manipulation)

Explore backtracking and bit manipulation methods to generate all subsets of an array. Learn efficient recursive and iterative techniques for subset generation.

- Tags: deep-dive
- Published: 2026-03-04

### [How to Solve the Paint House II Problem Using Dynamic Programming](/kdn251/interviews/paint-house-ii-dynamic-programming)

Solve the Paint House II problem efficiently with dynamic programming. Discover the O(nk) time and O(1) space solution by tracking minimum costs. Learn the optimal approach now.

- Tags: tutorial
- Published: 2026-03-04

### [Dynamic Programming Solution for the Decode Ways Problem: A Complete Guide](/kdn251/interviews/decode-ways-problem-dynamic-programming)

Learn the dynamic programming solution for the Decode Ways problem. Efficiently count valid letter interpretations of numeric strings in O(n) time using tabulation and a clear guide.

- Tags: how-to-guide
- Published: 2026-03-04

### [How to Implement Wildcard Pattern Matching for Strings in Java](/kdn251/interviews/wildcard-pattern-matching-strings)

Learn to implement wildcard pattern matching for strings in Java. Explore Trie and Dynamic Programming solutions for single-character and regex patterns from the kdn251/interviews repo.

- Tags: how-to-guide
- Published: 2026-03-04

### [Product of Array Except Self Without Using Division: O(n) Java Solution](/kdn251/interviews/product-array-except-self-no-division)

Calculate product of array except self in O(n) time and O(1) space using a two-pass algorithm without division. Learn the efficient Java solution.

- Tags: how-to-guide
- Published: 2026-03-04

### [Algorithm for Merging Overlapping Intervals: Greedy Implementation Guide](/kdn251/interviews/merge-intervals-overlapping-problem)

Master the algorithm for merging overlapping intervals with this greedy implementation guide. Achieve O(N log N) efficiency by sorting and combining.

- Tags: how-to-guide
- Published: 2026-03-04

### [How to Implement an LRU Cache with O(1) Time Complexity in Java](/kdn251/interviews/implement-lru-cache-o-1)

Implement an LRU Cache in Java with O(1) time complexity. Combine HashMap and doubly-linked list for efficient get, put, and eviction operations. Master cache implementation.

- Tags: how-to-guide
- Published: 2026-03-04

### [How to Find the Number of Islands in a 2D Grid Using DFS or BFS](/kdn251/interviews/number-of-islands-dfs-bfs)

Learn to find the number of islands in a 2D grid using DFS or BFS. Discover efficient graph traversal techniques to count connected land components and avoid double counting.

- Tags: how-to-guide
- Published: 2026-03-04

### [How to Solve the Word Break Problem Efficiently Using DP and Trie](/kdn251/interviews/word-break-problem-dp-trie)

Learn to solve the Word Break problem efficiently using DP and Trie. Achieve O(n·L) time complexity for faster solutions.

- Tags: how-to-guide
- Published: 2026-03-04

### [How to Implement Regular Expression Matching Using Dynamic Programming: A Complete Java Guide](/kdn251/interviews/regex-matching-dynamic-programming)

Master regular expression matching with dynamic programming in Java. Build an O(m x n) DP table to handle . and * efficiently. A complete guide for interviews.

- Tags: how-to-guide
- Published: 2026-03-04

### [Dynamic Programming Solution for the House Robber Problem: Complete Guide](/kdn251/interviews/house-robber-problem-dynamic-programming)

Learn the dynamic programming solution for the House Robber problem. Discover how to maximize loot without robbing adjacent houses using a bottom-up approach and recurrence relation.

- Tags: deep-dive
- Published: 2026-03-04

### [How to Validate if a Given Binary Tree is a Valid Binary Search Tree (BST)](/kdn251/interviews/validate-binary-search-tree)

Learn how to validate if a binary tree is a valid Binary Search Tree BST. Discover the depth-first traversal method with permissible value ranges to ensure BST integrity.

- Tags: how-to-guide
- Published: 2026-03-04

### [How to Find the Lowest Common Ancestor (LCA) in a Binary Tree](/kdn251/interviews/lowest-common-ancestor-binary-tree)

Learn how to find the Lowest Common Ancestor in a binary tree using a recursive DFS approach. Get the optimal solution for this common interview question.

- Tags: how-to-guide
- Published: 2026-03-04

### [Sliding Window Approach for Minimum Window Substring: Algorithm and Implementation](/kdn251/interviews/minimum-window-substring-sliding-window)

Learn the sliding window approach for Minimum Window Substring. Discover an efficient O(n) algorithm to find the smallest substring containing all characters of T using two pointers and hashmaps.

- Tags: deep-dive
- Published: 2026-03-04

### [How to Implement a Trie (Prefix Tree) for String Searching and Autocomplete](/kdn251/interviews/implement-trie-prefix-tree-autocomplete)

Implement a Trie prefix tree for efficient string searching and autocomplete in O(L) time. Learn how this data structure overcomes common limitations.

- Tags: how-to-guide
- Published: 2026-03-04

### [Longest Consecutive Sequence O(n) Solution: Hash Set Algorithm Explained](/kdn251/interviews/longest-consecutive-sequence-o-n-solution)

Discover the O(n) solution for the Longest Consecutive Sequence problem. Learn how hash sets optimize this algorithm for linear time complexity.

- Tags: algorithm-explanation
- Published: 2026-03-04

### [How to Perform Binary Search on a Rotated Sorted Array in Java](/kdn251/interviews/binary-search-rotated-sorted-array)

Master binary search on a rotated sorted array in Java. Find targets in O(log n) time by identifying sorted halves and narrowing the search space efficiently.

- Tags: how-to-guide
- Published: 2026-03-04

### [How to Solve the Maximum Subarray Problem Using Kadane’s Algorithm](/kdn251/interviews/maximum-subarray-problem-kadanes-algorithm)

Master the Maximum Subarray problem with Kadane's algorithm. Learn this efficient O(n) solution to find the largest sum subarray quickly. Improve your coding skills today.

- Tags: how-to-guide
- Published: 2026-03-04

### [How to Merge K Sorted Linked Lists: Efficient Min-Heap Methods Explained](/kdn251/interviews/merge-k-sorted-linked-lists-efficiently)

Learn efficient methods to merge k sorted linked lists using a min-heap for O(N log k) time complexity. Discover how to extract smallest nodes and optimize merging.

- Tags: how-to-guide
- Published: 2026-03-04

### [How to Detect a Cycle in a Linked List Using Floyd’s Tortoise and Hare Algorithm](/kdn251/interviews/detect-cycle-linked-list-floyds-algorithm)

Detect a cycle in a linked list efficiently with Floyd's Tortoise and Hare algorithm. Learn how two pointers moving at different speeds reveal loops.

- Tags: how-to-guide
- Published: 2026-03-04

### [How to Implement a MinStack with O(1) Push, Pop, and GetMin Operations](/kdn251/interviews/implement-minstack-constant-time)

Learn to build a MinStack for O(1) push, pop, and getMin operations. Discover how augmented nodes store minimums efficiently for faster retrieval.

- Tags: how-to-guide
- Published: 2026-03-04

### [Two Sum Problem: How to Solve It Efficiently with a HashMap in Java](/kdn251/interviews/two-sum-problem-hashmap-java)

Learn to solve the Two Sum problem in O(n) time using a Java HashMap. Discover an efficient algorithm for finding two numbers that add up to a target value.

- Tags: how-to-guide
- Published: 2026-03-04