More Essential LeetCode-Style Interview Questions

More essential LeetCode-style interview questions

Key Takeaways:

1. Pattern Recognition: Most problems fall into categories (e.g., sliding window, DP, BFS/DFS).

2. Space-Time Tradeoffs: Hashmaps, heaps, and memoization optimize time at the cost of space.

3. Edge Cases: Always test empty inputs, single-element cases, and duplicates.

1. Reverse a Linked List (Linked List)

Problem: Reverse a singly linked list.
Approach: Iterative (three pointers) or recursive.

2. Find Median from Data Stream (Heap)

Problem: Design a data structure to find the median of a streaming data set.
Approach: Use two heaps (max-heap for lower half, min-heap for upper half).

3. Trapping Rain Water (Two Pointers)

Problem: Compute how much water can be trapped between bars of different heights.
Approach: Two pointers tracking left/right max.

4. Course Schedule (Topological Sort)

Problem: Check if you can finish all courses given prerequisites (detect cycles in a graph).
Approach: Kahn's algorithm (BFS with in-degree tracking).

5. Longest Palindromic Substring (DP)

Problem: Find the longest palindromic substring in a string.
Approach: Expand around center or DP table.

6. Search in Rotated Sorted Array (Binary Search)

Problem: Search for a target in a rotated sorted array.
Approach: Modified binary search to find pivot.

7. Subsets (Backtracking)

Problem: Generate all subsets of a distinct integer array.
Approach: Backtracking or bitmasking.

8. Serialize and Deserialize Binary Tree (Tree)

Problem: Convert a binary tree to a string and reconstruct it.
Approach: Preorder traversal with "null" markers.

9. Minimum Window Substring (Sliding Window)

Problem: Find the smallest substring in s containing all characters of t.
Approach: Sliding window with hashmap for counts.

10. Edit Distance (DP)

Problem: Find the minimum operations (insert/delete/replace) to convert word1 to word2.
Approach: DP table with dp[i][j] representing subproblems.